I think I may found the problem, probably it's a bug.
So, like stated before, going to Restore tab -> job name = no results on the box where the file list should be.
If I go on the Job and on the last job of that client I click on the restore icon, it redirects me to the restore tab but this time the files are there.
So:
Restore -> Client -> NO files
Jobs -> backup-job -> restore -> OK files.
Maybe it's something with a previous job because when I select NO to "Merge all client filesets" then I see the files.