it is one of the possibilities (either ... or...)
Maybe you wanna try to list what Catalog is available:
omnidb -winfs <Host>:<Mount> <Description> -session <SessionID> -catalog
If that shows an empty result you will not be able to see anything in Restore-Browser either.
If that is the case you have to import the Catalog and try again after it completed.
Devices & Media -> Select Media -> Import Catalog.