The backup disk image “MacBook Pro (2).sparsebundle” could not be accessed (error 19).

Courtesy of Bob Timmons, another frequent Community contributor: Hold down the option key on your Mac while you click on the Time Machine "clock" icon at the top of the Mac's screen. Select Verify Backups and run the process. If the process can run, it might take anywhere from 10-60 minuted for the check to complete. You can watch the progress by clicking on the Time Machine "clock" icon and then clicking on Open Time Machine Preferences

If the process cannot run, or errors are reported, unfortunately this would indicate that either your backup file has become corrupted and/or the backup drive is failing. In either case, that backup is probably lost.

Hope this helps.

MacBook Pro (2) suggests Time machine has become confused at not being able to access the original sparsebundle, and may have even tried to create another, which may also be inaccessible.

You also need to be certain the network drive is accessible in Finder, and has not dropped off the network for any reason.