My Passport for Mac

Easiest solution is to reformat it: Erase and reformat a storage device in Disk Utility on Mac - Apple Support

I'd also recommend renaming the external drive before backing up to Time Machine.

Hope this helps.

Is this a brand new drive?

If it is labeled as for Mac use, then all you should need to do is connect it to the computer and use it.

If you have already been using it, then there is no "update" needed.

Are you having some problem using it?

What exactly are you trying to accomplish?

Are you using Time Machine for backups?

And did you erase and format the drive before using it? The WD software installed by default is worthless and can cause havoc so it is best to erase it. External drives do not need software or drivers to function.

What is the available space on the backup drive?

What is the available space on the startup drive?

I would first run the Disk Utility First Aid routines on the backup drive. If DU gives the green light, then...

...in the Time Machine settings, select the drive and remove it from use by clicking the Minus (–) button below it. TM will ask if you want to forget the drive, so confirm that. Don't worry, you're going to add it right back, and that won't affect the existing backups.

So add the drive back to TM by selecting it and clicking the Plus (+) button. Confirm it if asked, and TM will begin to use the drive again, likely starting another regular backup.

Hopefully this will shake out the cobwebs and allow the regular backups to start again.

+1 👍🏽