Wow, looks like this person is having the exact same issues as me:
https://wp-dreams.com/forums/topic/cant-turn-on-plugin/
Mine did the same, open_basedir errors then it filled up the error_log in /wp-admin/ – that is why this guy had exceeded his disk quota. After I tried Activating the plugin 5 times – the error_log file was 3.6Gb!!!!