Reset plugin folder via FTP
Navigate to the wp-contents directory via FTP.
Rename plugins folder to “plugins-temp”.
Create a new folder called “plugins” at wp-contents.
Try to login to your WordPress wp-admin.
Move your plugin from “plugins-temp” to “plugin” and activate them one by one.
Check if any plugin is not compatible with your version of WordPress.
or
Navigate to the wp-contents/themes directory via FTP.
Rename current installed theme folder. For example: “twentytwenty” to “twentytwenty-temp”.
Login to your WordPress wp-admin.
Check if your theme is compatible with your version of WordPress.
Check if your theme contains coding which can’t be executed.
This did not work for me. Please help.