White Screen of Death affter failed plugin activation

I have suddenly experienced the White Screen of Death after trying to activate the WP-Optimize plugin. The activation failed and displayed an error and after this wp-admin is no longer accessible.

The front end and the login screen are both accessible however all wp-admin pages return a blank screen.

I have checked the activated plugins through phpmyadmin and wp-optimize was not listed there.

I also deactiated all plugins through phpmyadmin however the issue persisted.

I have backed up all the wp-admin files and transfered a clean copy of these to the server (with appropriate wp-config.php settings) and the issue has still not been fixed.

When renaming the theme I am using to another theme, the wp-admin still does not work and neither does the front-end.

I am completely lost on what to do next.