The session of one of my accounts (not even the one I was trying to use) had its session expired. This seems to be new. I just had to re-sign in to the errant account in Xcode > Preferences > Accounts.
The session of one of my accounts (not even the one I was trying to use) had its session expired. This seems to be new. I just had to re-sign in to the errant account in Xcode > Preferences > Accounts.