My PrestaShop shows a blank white page, how do you fix it?

The PrestaShop white screen of death means a fatal PHP error is being swallowed because display_errors is off. We enable debug mode safely (set _PS_MODE_DEV_ or use the back-office advanced parameters), read the real fatal from var/logs/, and fix the root cause, a bad override, a missing class, a memory limit, or a corrupt var/cache. Then we turn debug mode back off and clear the cache so the live shop renders clean.