Removed a client, can't add it back again

One of the clients I had was misbehaving: It wouldn’t end a backup correctly. It would reach 100% but as if nothing happened, the computer showed as not backed-up.

So, I decided to start over, mark it for removal, remove it manually from the server’s console (urbackupsrv cleanup -a “0%”) and uninstalled the client as well.

Then, I reinstalled the client, but after an hour or two, it still didn’t appear on my server.
Went ahead and added it manually: After another hour, it still isn’t showing up.

Is that device somehow blacklisted or something?

What’s the best course of action to re-add a deleted client?

EDIT: Restarted both client and server and now the backup is running, and working better than before.