Obeya says when the phone's app has an old address

Obeya on a phone's home screen keeps the address it was added at. Once Obeya's address changes (the computer renamed in Tailscale, another port, another address), that app got no answer and gave no reason. Now “Connect a phone” and the settings for other devices say which phone's app still opens an old address and how to fix it: delete the app, scan the new code, add Obeya to the home screen again. Connecting the phone again replaces its old entry, and the phone's own “not answering” notice mentions a changed address as a possible reason.