Time Machine: "No macOS system backups were found"

Hey audio_kudos,

If we understand correctly, you upgraded to macOS Big Sur, made two backups, then you reverted to macOS Catalina and now you want to use those backups in Catalina. There are a couple things you can try that may be able to help. We would recommend you read these articles for more information.

If you can't back up or restore your Mac using Time Machine

If Time Machine on your Mac can’t find your backup disk

Please don't hesitate to let us know if the steps resolved your issue or if you need additional assistance.

Thank you for using Apple Support Communities. Have a good one.

audio_kudos wrote:

I updated to Big Sur and wanted to downgrade back to Catalina. I made a bootable drive and stored all my data on an external hard drive via Time Machine. I successfully reinstalled Catalina on my mac but when I try to access Time Machine, I get this message, "No macOS system backups were found".

There are precisely 3 different back ups on my external hard drive and I have no other idea why Time Machine does not recognize it. The time machine back ups were made on Big Sur and I am trying to retrieve it on Catalina so that might be a reason but I am not sure.

Any help is appreciated.

How to reinstall macOS from macOS Recovery - https://support.apple.com/en-us/HT204904

Revert your Mac to a previous macOS version
https://support.apple.com/en-lamr/guide/mac-help/mh15216/10.15/mac/10.15