Common Magento Issues and How to Fix Them

After supporting Magento stores since 2008, the surprise isn't how many things can go wrong - it's how often it's the same short list. Here are the issues we see most, what actually causes them, and the fix.

500 errors and the white screen

Usually one of: PHP memory exhaustion, corrupted generated code, or file permissions after a bad deploy. Check the exception log first (var/log/exception.log), clear var/generated on staging and re-deploy compiled code properly. If it appeared right after a deploy, the deploy is the cause - roll back first, diagnose second.

Checkout or payment failures

The most expensive failure mode, and usually a conflict: a payment gateway module update, an extension patching the checkout, or an expired API credential. Reproduce it in an incognito session with a test card before touching anything - half of reported checkout bugs are actually a single payment method failing quietly.

Cron stopped running

When emails stop sending, indexers pile up, and scheduled prices never apply, check cron before anything else. It fails silently and takes half the platform's plumbing with it. Verify the crontab exists, then look for a stuck job holding the queue.

Extension conflicts after an update

Two modules patching the same class, or one module built for an older core. The tell is a feature that broke the same day something else was updated. The fix is isolating the pair on staging - which is also the argument for having staging at all.

Cache and Redis trouble

Stale prices, phantom content, sessions dropping: usually a cache that isn't flushing correctly or a Redis instance out of memory. Check Redis eviction settings - a session store evicting keys logs customers out mid-checkout.

Signs the store is compromised

Unfamiliar admin accounts, JavaScript you didn't add on the checkout, or customers reporting card fraud. Stop and treat it as an incident: malware scan, patch the entry point, restore from a clean backup. Speed matters more than tidiness here.

If an issue on this list is costing you sales right now, that's what our Magento bug fix service and emergency support exist for - a developer on it within 3 hours. And most of these are preventable: the same failures come up again and again on stores without routine patching and monitoring.