Macbook won’t add drive to time machine
I have a new WD Passport for Mac. I am trying to add it to Time Machine where I already have a similar drive set up. The drive is connected to my MacBook - its indicator light is is on. But when I select + to add the drive I get this message ‘No available time machine destinations. Connect a suitable external drive or network storage device.’ The Set Up Disk is greyed out.
Advice would be most welcome.
MacBook Pro 13″, macOS 11.7