Hello. My instance is mindly.social. It used to work fine, but now, when I try to connect, I simply see a Mastodon logo. This is true on both Firefox and Chromium browsers. However, when I use Pachli on my phone, it does connect. I'm not sure what the issue is.
It is likely they pushed a faulty update and it will eventually get resolved.
You may want to notify your admin via email if possible.
As the other user said, you can check the browser's dev console for specific errors to try to diagnose the problem.
The app still works because the website and app API are separate and the problem you are seeing appears to be related to how the page is rendered, not core functionality