Usual My Passport Drive - Read Only on MAC Now

I am using the My Passport for several years has worked as a back up with Time Machine on my Mac but now does not make me back up as it tells me that the My Passport external support is read-only. How do I? Why is it gone read-only after several years?
Many thanks

Hello Doman1960, have you recently changed the format of the Passport? If you have it formatted on NTFS (Windows format), it will only be read only on your Mac. You can also try running a test using Disk Utility.

How to test a drive for defects or problems on a Mac 

No I did not do anything.
The last thing I did with the My Passport external drive was a back up with time machine from my mac. Everything here …

I really do not know what’s appened…

Did you tried running the disk Utility test?