A plugin conflict is most likely when a problem begins immediately after installing, activating, or updating a plugin, but conflicts can also appear after WordPress, PHP, or another plugin changes.
- Create a backup or use a staging copy when available.
- Review the error log for a plugin file named in the fatal error.
- Deactivate the suspected plugin and retest.
- If the cause is unknown, deactivate plugins methodically and reactivate them one at a time until the symptom returns.
- Check the plugin’s current requirements before re-enabling it.
If wp-admin cannot load, WordPress documents renaming the plugins directory through FTP or a file manager as a way to deactivate plugins without deleting their settings.
While the folder remains renamed, visit /wp-admin/plugins.php so WordPress records the missing plugins as deactivated. Then restore the original folder name and enable only the intended plugins one at a time. Keep a recovery copy and account for temporarily unavailable forms or other plugin features.
Documentation for this guidance: wordpress.org — faq troubleshooting.
