13.0 and backups?

Ever since the upgrade to 13.0 three days ago, Jetpack has failed in its nightly backup: “We could not back up your site because it appears to be offline.” So, three times in total.

This could be a coincidence, but I’m guessing that it probably isn’t because it had been fine until 13.0. I don’t see anything in the release notes about it, however. Is it plausible? I’d like to eliminate that angle before investigating others.

Yes, VaultPress Backup is still listed as “Active” on our site. Yes, the site is active. No, I’m not aware of any changes from Cloudflare or Wordfence or our host which could also cause this, but that’s where I’ll look next depending on the above answer.