This usually happens when the Local Fee Finder plugin clashes with some other plugin you already had installed.
Try the following:
- Go to your Cpanel > File Manager > Public html > WP content > Find the "Plugins" folder and rename it. For example, call it plugins123
- Now you will be able to login to your WordPress backend.
- Deactivate all the plugins and then go back to your Cpanel again rename the plugin folder back to "Plugins"
- Test each plugin by activating one by one in the WP admin area.