Won’t activate

I’ve tried installing and activating this plugin ready for when Gutenblerg is forced on us but, although I can install the plugin (and it shows in the list of plugins on my website), it won’t activate. I click “Activate” and the plugin page refreshes and says “Plugin Activated” but it’s still showing in the list as deactivated. Likewise, there are no settings where I would expect to see them.

For reference, the plugin installed fine on two other websites I run without issue. The only difference is, on those, I installed (and activated) from the Gutenblerg nag screen whereas on this site I used the Plugin > Add New interface.

Thanks for any help you can provide because I do not want to use Gutenblerg.