Stuck in Maintenance Mode

After setting up the plugin at our multisite installation, subsites where it wasn’t even activated are stuck in maintenance mode, even after the plugin is deactivated and disabled.

I’ve not just cleared but de-activated the site cache, paused Cloudflare, and cleared browser caches. Still stuck, on separate browsers. I’ve also tried rolling back the plugin to previous versions.

Next I’ll try turning off all plugins and switching themes. This is an active e-commerce and e-learning site, and a complete disaster.