Teams opens an old meeting on launch

[ErinFErinFErinF]

I had a meeting with my child's school months ago, and now every time I launch MS Teams a window of the expired meeting opens with giant confusing UI. My company instance of MS Teams also opens, in a separate window. It's confusing and annoying to close the old glitchy window on every launch. How can I stop this from happening?

I'm running macOS Catalina 10.15.7. I can't tell which version of Teams I'm running because when I go to "Microsoft Teams -> About Microsoft Teams" either nothing happens, or the glitchy window opens :face_with_tears_of_joy:

Giant UI of expired meeting

Weird Giant UI

[#2 · Accepted solution]

I've managed to fix this by signing out by right-clicking the Teams icon in my doc, signing out, and then deleting the App data folder in my Library as described here.