Three copies, two media, one off-site. I set up my 3-2-1 backup, checked every job twice and started the first upload to the cloud.
A few minutes later, from another room: THE INTERNET IS DOWN!
The backup was working perfectly. That was exactly the problem.
How it went, and what's still missing:
https://kr0x7c0.sh/en/posts/3-2-1-backup/
Have you ever actually tested a restore from your off-site copy?