A blank white page or "There has been a critical error" usually means a PHP error — often a memory limit or a plugin conflict.
Try these in order:
1. Increase PHP memory. Ask your host to raise it to at least 256M, or add "define('WP_MEMORY_LIMIT', '256M');" to wp-config.php. 2. Enable error logging: set "define('WP_DEBUG', true);" and "define('WP_DEBUG_LOG', true);" in wp-config.php, reload the page, then read wp-content/debug.log to see the exact error. Turn debug off again when done. 3. Rule out plugins: rename the wp-content/plugins folder to plugins-off via FTP/File Manager to deactivate all plugins at once. If the site returns, rename it back and re-activate plugins one by one to find the culprit. 4. Confirm your PHP version meets the theme's requirement (PHP 7.4+ for most, 8.0+ recommended).
If you're stuck, open a ticket and paste the exact error line from debug.log — that tells us precisely what failed.