I've seen a post going around but I can't find it, so I'll recap: uBlock Origin and it's ilk have a rule that breaks loading some of the mastodon components for some instances (idk if it affects mainline masto?)
Ours is one of those instances - it seems to manifest in that you can't open a thread, you'll get an error when you click on a toot to 'zoom in' as it were.
If that's the case, just add an exception or disable uBlock on mastodon.mania.systems and the problem should go away.
Mania Systems is a space for independent, underground, and non-traditional artists & creatives to share their work, meet each other, and collaborate. This mastodon instance is one community space we offer - a decentralized social network, run by the community, where you own your data and the content you post.