Back restore to Mojave from Catalina and lost time machine backups and capability to backup

Toolhog wrote:

Unfortunately, I am not a tech savvy person and all the items listed above seem to me to have needed to be done before the actions that lead to my predicament. The time machine will not back up my computer after restoring Mojave and I can't find any settings that will let me change anything that will. If someone could lead me through some steps that would be much appreciated.

From the original Help topic:

"You can move the backup history from one Mac to another, but after the new Mac “inherits” the backup history, you can’t use the backup history on the original Mac."... that is saying the old macOS..

So you reverted back to Mojave and lost all the inherited BU.

You can reformat the backup drive from Disk Utility and start a new backup.

Part of a robust backup plan is to have more than one backup, more than one method—in this way if one backup method fails, you continue to have options.

How to erase a disk for Mac - Apple Support

Backup disks you can use with Time Machine - Apple Support

https://support.apple.com/guide/mac-help/types-of-disks-you-can-use-with-time-machine-mh15139/mac

Toolhog wrote:

I restored my Macbook Pro backwards to Mojave from the new Catalina to be able to use old Microsoft software. In doing so I must have done something wrong because although I restored my laptop and use of Microsoft software, I now can't back up to the Time Machine nor are there any old backups available for my laptop. The Time Machine is not even listed as a drive in Finder anymore. Need help undoing something, while keeping older OS.

Thanks in advance for any assistance.

* https://support.apple.com/guide/mac-help/if-your-new-mac-inherits-your-backup-history-mh35732/mac

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

Boot clone https://discussions.apple.com/docs/DOC-10081

How to use Time Machine to back up or restore your Mac: https://support.apple.com/en-us/HT201250

Use DiskUtility Restore feature https://support.apple.com/guide/disk-utility/restore-a-disk-dskutl14062/mac