This usually happens when the Local Fee Finder plugin clashes with some other plugin you already had installed. 

Try the following:

  1. Go to your Cpanel > File Manager > Public html > WP content > Find the "Plugins" folder and rename it. For example, call it plugins123
  2. Now you will be able to login to your WordPress backend.
  3. Deactivate all the plugins and then go back to your Cpanel again rename the plugin folder back to "Plugins"
  4. Test each plugin by activating one by one in the WP admin area.