Time Machine not backing up

Bernie Renton wrote:

I recently installed a new 4 TB ssd drive. to use as a Time Machine drive.

The drive was ejecting while in sleep.

I turned off sleep mode and reformatted ssd drive.

Now I am getting the following error:

Time Machine couldn’t complete the backup to “Time Machine”

“/usr” could not be backed up.

See if there is something here... GUID (partition map) / APFS (file type)

Erase and reformat a storage device in Disk Utility on Mac

Erase and reformat a storage device in Disk Utility on Mac - Apple Support

Back up your Mac

Back up your Mac with Time Machine - Apple Support