Time Machine has stopped backing up my Macbook Air.
Hello. I cannot backup my Macbook Air on Time Machine. It sticks on 'preparing backup' The last backup was a couple of months ago and I had no problems with it at the time. I have recently backed up another mac onto the external drive I'm using with no problems.
It's an old machine, 13" 2015 OS 10.14.6
MacBook Air 13″, macOS 10.14