If this article does not resolve your issue, you can open a support ticket or visit https://codex.wordpress.org/Common_WordPress_Errors
While the most common cause of this problem is memory exhaustion, it can also be caused by a problematic theme or plugin.
- Increase the PHP memory limit (see Fatal error: memory exhausted)
- If the issue persists, disable all your plugins by renaming the wp-content/plugins/ folder
- If the issue persists, change your active theme
If your issue is still not resolved, check the error logs for your domain in Sites and Databases > Domains.