Is your Cell Manager UNIX or Windows?
The confounding thing about this is when you try to expand 'Restore Sessions' and there is nothing there. To me, this indicates a possible problem with the IDB (Internal DataBase)
Lets see if we can list the sessions a different way. From the command prompt on the cell manager, run
omnidb -session -type backup -last 5
which should give you a listing of backups for the last 6 days, including session IDs. If you want to filter this list for one backup specification, you can include the '-datalist' argument, for example
omnidb -session -datalist "Exchange Daily" -type backup -last 5
In this example, the name of the sample backup specification needed to be enclosed with " marks because there was a 'space' in the name of the backup specification
You can alter the number of days if you want, or, it can be run with a date range