The majority of WooCommerce issues that aren’t configuration mistakes are caused by conflicts — a plugin interfering with another plugin, a theme overriding expected behavior, or a combination of both. Conflict testing isolates the cause.
Step 0: Set up a staging site. Never conflict-test on a live store. Your host likely offers staging. If not, use WP Staging.
Step 1: Permalink refresh. Settings → Permalinks → Save Changes. You’re not changing anything — just regenerating rewrite rules. This fixes a surprising number of “broken page” and “404 on checkout” issues in five seconds.
Step 2: Deactivate all plugins except WooCommerce (and your payment gateway if testing checkout). Test the issue. If it’s gone, the cause is one of your deactivated plugins.
Step 3: Reactivate plugins one by one, testing after each. When the issue returns, you’ve found the conflict.
Step 4: If the issue persists with all plugins deactivated, switch to a default theme (Twenty Twenty-Four). If resolved, your theme is the cause.
Step 5: If it persists with all plugins off AND a default theme, the problem is hosting, WordPress core, or WooCommerce core (rare). Check WooCommerce → Status → System Status for red flags and contact hosting.