Backup failed and attempts to reach the website timed out. Everything else worked fine, even Google worked without popping up a captcha.

Turns out iDrive is blocking certain IPs used by my VPN (Mullvad)... no message, just a timeout. I switched to a different VPN location and it worked fine.

It seems to me that even if a bad actor has caused an IP address to get blocked, the right response would be some type of message (as opposed to a timeout).