Plus, I don’t really want to delete my old backup until I figure out what’s going on. If I DO need something on that old backup, then I’m really out of luck.
I do not what to tell you. I just ran a back up to test. It does run and simply opens when it is working properly. What is the harm of deleting the old back up if you system is working fine? If the program does not open anyway you are not really using the back up and can not make a current back up.
But again your choice.
Look in C:\ProgramData\Western Digital\Logs\WD Backup<UserName> for an error in the log file.
You probably have a bogus backup plan that causes the error.
Look in C:\ProgramData\Western Digital\Logs\WD Backup<UserName> for files with names similar to the bad backup plan and delete them! (move them somewhere else, if you’re skeptical)
Retry the backup.