When locally debugging my Teams meeting App, app gets added and then disappears immediately.

I'm currently running my app on https://localhost with trusted certs, not using Teams Toolkit. Channel / Chat context works as expected, but when trying to add my App to a meeting, after I save settings, the meeting shows up in the Chat for a few seconds, and then disappears.

When joining the meeting, the app says it's there on the panel, but when trying to open the side panel, it does nothing but spin.