Why do my customers say they can't browse, add to cart, or check out on my store?
When shoppers report broken browsing, carts, or checkout all at once, the cause is almost always isolatable, whether that's a bad app script, stale theme code, a browser quirk, or a rare platform incident, if you test methodically instead of guessing.
What's going on
You're getting messages from customers, or seeing it yourself, that something is broken end to end: product pages won't load properly, items won't add to cart, or checkout hangs, errors, or won't complete. It can feel like the whole store is down, but customers can't buy anything is rarely one single failure. It's a symptom that several different things could cause, and the fix depends entirely on which one it actually is.
The frustrating part is that these issues are often intermittent or device-specific. It might work perfectly for you on your laptop while a customer on mobile gets stuck, or it might fail only after a particular app updates its script. That inconsistency is actually useful diagnostic information: a failure that's fully reproducible for everyone points to your theme, your apps, or Shopify's own infrastructure, while a failure that only some customers hit usually points to something on their end, such as their browser, cache, extensions, or network, rather than your store setup.
Because browsing, cart, and checkout span several different systems, including theme rendering, cart requests, third-party app scripts, and Shopify's checkout, the right first move isn't to assume you know the cause. It's to reproduce each stage separately across a couple of environments so you can narrow down where the chain actually breaks.
Why it happens
The most common root cause is a JavaScript conflict: a theme customization or an installed app injects a script that throws an error, and that error can halt other scripts on the page, including the ones that power add-to-cart buttons or checkout redirects. Because browsers process scripts in order, one broken script can silently break unrelated functionality elsewhere on the page.
The second most common cause sits entirely on the customer's end: stale cached files after a theme update, an aggressive ad blocker or privacy extension blocking storefront or payment scripts, or an outdated browser. These produce alarming-sounding reports, such as nobody can check out, but they only affect the specific customers who reach out, while the store works fine for everyone else.
Less frequently, the cause is a genuine platform-side event. Shopify's checkout and storefront infrastructure occasionally has short incidents, and a payment provider can have its own outage, and both can produce symptoms that look identical to a store-specific bug from the merchant's side.
5 ways to fix it
Reproduce it yourself in an incognito window and a second device
Before touching anything in your store, try to reproduce the exact problem in a private or incognito browser window, then on a second browser and a mobile device. A large share of nothing-works reports trace back to one customer's stale cache, cookies, an ad blocker, or a browser extension interfering with scripts, not a store-wide bug. If it works cleanly for you across devices, the fault is most likely client-side for that shopper rather than a problem with your store configuration.
Rule out a platform-wide Shopify or payment provider incident
Check status.shopify.com for any active incident before you start changing theme or app settings. Shopify's infrastructure occasionally has brief regional or global disruptions that affect many stores' storefronts or checkouts at once, and those resolve on their own with no action needed from you. Also check with your payment provider directly, since a provider-side outage can look identical to a store-side bug from your end. If nothing is reported and the issue is isolated to your store, move on to the theme and app checks below.
Isolate theme code by previewing a default theme
From your theme settings, duplicate your live theme so you have a safe copy, then preview a stock theme (such as Dawn) and try browsing, adding to cart, and reaching checkout on it. If everything works on the default theme, the cause is very likely custom theme code, such as a broken template edit or a JavaScript error blocking the add-to-cart button. Shopify's theme code editor keeps a version history you can use to review or revert recent changes. If the default theme also fails, the problem isn't your theme and you can rule it out.
Disable apps one at a time to find a script conflict
Go to your apps list and deactivate installed apps one at a time, especially any that inject cart drawers, upsell widgets, tracking pixels, or other scripts into storefront pages, retesting the customer flow after each one. App-injected JavaScript is one of the most common causes of intermittent cart or checkout failures, because a script error from one app can silently stop other scripts on the page from running, including the ones that power your cart or checkout buttons. Once you find the culprit, re-enable the others and contact that app's support for a fix or update.
Check your checkout and payment settings for misconfiguration or blocks
If the failure is specific to checkout rather than browsing or the cart, review your checkout and customer account settings for anything recently changed, and confirm your payment provider is connected and not flagging an issue that requires reauthorization. Also check whether a fraud filter, checkout rule, or shipping restriction could be unexpectedly blocking certain orders. These settings are easy to overlook because they fail silently for affected customers while working fine for everyone else.
Bottom line
Most nothing-works reports turn out to have one specific, findable cause, whether that's a browser quirk, a stale cache, one misbehaving app script, broken theme code, or a genuine but brief platform incident, rather than a single catastrophic failure. Work through the isolation steps above in order rather than guessing, since the fix depends entirely on which cause you're actually dealing with. If you land on a specific bug you can't resolve yourself, a Shopify Partner or agency comfortable debugging theme and app conflicts can usually diagnose it faster than back-and-forth with app support, since no single app can fix a problem whose cause varies from store to store.
Browse the rest of the problem library, run a free storefront scan to catch issues like this automatically, or email us and we'll work out a custom solution for it.