iCloud email disappears from inbox, replaced with "All Done"

I am a new Mailspring user and just installed the current release on Windows 10. Everything seemed fine then after maybe 15 minutes all the email in my iCloud inbox disappeared and a message saying “All done” replaced the email.

I looked in every folder and found nothing so I uninstalled and reinstalled Mailspring with the same result.

There must be something simple I’m missing. Please advise.

That’s a really weird bug. It reminds me of Protonmail: All emails disappear from inbox (and reappear, then disappear again...) … but that’s Prontonmail, and this is iCloud? Hm.

Are the emails actually being removed from your inbox folder (it would show up as such in the iCloud web client), or does Mailspring just act like that’s the case?

Has anyone else seen this happen?