This page is organised by symptom. Find the thing that is happening to you, read the cause, apply the fix. Almost every problem merchants hit with this app has one of a small number of causes, and the great majority are a gate that has not been satisfied rather than a fault.
What you see: "This app must be opened from your Shopify admin (Apps, Amazon Price Sync)." or "Could not authenticate with Shopify. Please reload the app from your Shopify admin."
Cause. The app is an embedded Shopify app. It only works inside your Shopify admin, where Shopify hands it a session token that proves who you are. Opening it from a bookmarked URL, a saved tab, a link in an email, or a browser window where your Shopify session has expired gives it no way to authenticate you.
Fix. Go to your Shopify admin, open Apps, and launch Amazon Seller Sync from there. If you were already inside the admin and it still fails, your session has simply gone stale. Reload the page. If it persists, log out of Shopify and back in.
Tip
Do not bookmark the app's URL directly. Bookmark your Shopify admin's Apps page instead.
What you see: "Missing: {scopes}. Reopen the app to re-authorize." The Settings > Automation tab also warns you when scopes are missing.
Cause. Scopes are the permissions Shopify grants the app: to read products, to write inventory, and so on. Occasionally the app needs a permission it was not granted at install, typically because you have upgraded, or because you are turning on a feature such as Fulfilment by Amazon that needs permissions the app deliberately does not ask for until you use it.
Fix. Close the app and open it again from your Shopify Apps menu. Shopify will show you the permission prompt. Approve it. The app cannot request permissions while it is already running, which is why reopening is the fix.
If you see "Permissions were declined. They're needed to manage Amazon fulfilment and tracking.", you clicked away from the MCF permission prompt. Reopen and accept it. Without those permissions the app cannot fulfil your orders through Amazon.
Cause. No Amazon account is connected. There is nothing to sync from, so the button is disabled rather than failing.
Fix. Go to Settings > Amazon account and connect an Amazon Seller Central account. If an account is listed but the button is still disabled, its authorisation has likely lapsed. Use Reconnect. See Connecting Amazon.
Cause. The app does not currently publish products to Amazon, and there is no screen for it. This is a deliberate change, not a fault or a missing permission, and it is not something a higher plan unlocks.
What the app does instead. Data flows from Amazon into Shopify, not the other way. You map a Shopify variant to an Amazon ASIN on the Product Mapping page, and the app reads that product's Amazon price and your Buy Box status back into your store. Your Shopify product content is yours to improve on the Listings page, and it saves back to Shopify.
If you need Amazon listings created, do it in Seller Central. Once a listing exists there, you can map your Shopify variant to its ASIN and the app will track its price for you as normal.
The Buy Box repricer is not currently offered either, for the same reason. See the FAQ.
Cause. Usually the Choose your marketplaces step. It completes only when you have explicitly saved a market mapping. A marketplace that the app inferred from your connected Amazon account does not count, even though the app is clearly using it.
Fix. Go to Settings > Markets, choose your default (home) marketplace, and save. The step ticks.
The other steps are more literal: connect an account, acknowledge the conflicting apps check, and map at least one product. See The setup checklist.
Work through these in order.
The variant is not mapped. Price sync only touches variants that have an ASIN attached. On the Product Mapping screen, filter to Needs mapping and see if your product is sitting there. Map it, or run Auto-match one-to-one if it has a barcode.
The sync interval has not elapsed. Free syncs every 24 hours. Paid plans sync every 6 hours. If you mapped a product ten minutes ago, its price simply has not been fetched yet. Click Sync now on the Dashboard to force it.
Amazon has no offer. If nobody is currently selling that ASIN as New, there is no lowest offer for the app to fetch, so there is no price to write. The product will show as having no price and this is correct, not a bug.
The barcode is wrong. Auto-match matches on barcode alone. A wrong barcode maps you to the wrong ASIN, and you get a real price for the wrong product. If a price looks bizarre, check what ASIN the variant is mapped to. See Auto-match.
The app does not manage a listing for that product. Inventory Sync writes stock into Amazon listings the app manages. A product that is only mapped for price sync appears in the read-only Price-mapped products card, and no stock is written for it in either direction.
The SKU is FBA, not FBM. The app detects fulfilment type per SKU. If the SKU appears in Amazon's FBA inventory, Amazon holds the stock and the app treats it as read-only. It will show you Amazon's availability but it will never write to it. Only merchant-fulfilled (FBM) SKUs are pushed. This is correct behaviour, not a limitation.
Inventory Sync is a paid feature. It is available from Growth upwards. On Free you will not have it.
If none of those apply, note that FBM push is not on a schedule. It fires within seconds of a Shopify stock change. If your stock has not changed recently there is nothing to push. Force it with Sync all FBM inventory. See How FBM stock reaches Amazon.
Cause. The app does not change your Amazon prices. It reads them.
There is no repricer in the app today, and no per-product price override. Price sync is one-directional: Amazon's price and your Buy Box status come into Shopify, and nothing about your Amazon offer goes back. If you want to change what you charge on Amazon, do it in Seller Central.
Your Shopify prices are equally safe. The app has never written to them and does not now. See Price sync.
Cause. The button hides itself entirely when no URL resolves for that product in the shopper's market. It is designed to disappear rather than render a dead button.
Fix. Check, in order: is the variant mapped to an ASIN at all; has a price sync run since you mapped it, since the Amazon URL is written by the sync; and is the shopper's market mapped to an Amazon marketplace. On the Free plan you get only the default marketplace, so a shopper in an unmapped market falls back to your home marketplace link.
You can also set an override URL, either store-wide or per product, under Buy on Amazon. See Buy on Amazon button.
Cause. Buy Box history is recorded on each price sync. It is not fetched retrospectively from Amazon, because Amazon does not hand out that history.
Fix. Wait. The report fills in as syncs happen. On Free, at one sync a day, a 30-day report takes 30 days to fill. On a paid plan at 6 hours you build a useful picture within a few days. Nothing is broken; the data simply has to accumulate. See Analytics.
Symptom. Prices or stock levels on Amazon flap back and forth, changing to one value and then to another shortly afterwards.
Cause. Two apps are managing the same Amazon listings and are overwriting each other. The app checks for this on setup and detects the common ones, including Codisto, CedCommerce, ByteStand, Sellbrite, SellerCloud, Reputon and Shopify's own Amazon sales channel.
Fix. Decide which app owns which function and turn the other one off for that function. The Is another app managing your Amazon? modal lets you tick which functions another app handles (Pricing / repricing, Inventory & stock sync, Creating / editing listings, Fulfilment (FBA / MCF)), and after you have disabled them in the other app you click I've disabled these, recheck.
The check is a warning, not a hard block, so you can override it and continue. Be aware of what you are choosing if you do. See Conflicting apps.
If your problem is not here, the two most useful things to gather before asking for help are the exact error text the app showed you, and which plan you are on. A large share of "it does not work" reports resolve to a paid feature being used on the Free plan.