My Passport Will NO Longer Back Up!

I’m sure this has been covered somewhere in here, but I have two 2TB My Passports that I use as back-ups for my hard drive. The Time Machine has been backing up no problem, then all of the sudden yesterday it no longer works. I’ve read posts about the hard drive not being formatted for Mac, but that can’t be the case here since it’s been backing up for about 6 months with no problems. I checked in the permissions and it says “read only”, even though as the administrator it says “read write”. And after I unlock as the administrator it won’t allow me to change any of the permissions. So what’s up? Why suddenly changed? I don’t want to erase these drives and start again, so there has to be a solution.
Thanks.

Hello there,

Try to do a get info on the drive, then try to check the permissions on the device see if you can change them to read and write.

Nope, it won’t let me change the permissions, even though I can sign in as the admin.
So it’s really down to one big question. Why did two identical drives that were backing up with no problems, suddenly decide they could no longer back up?