Candidates not visible to firm user: If you can see a candidate in the assignment candidate list, but not in the portal, it may be that the candidate has been marked as ‘Off Limits’ (there will be a red flag icon on the profile). Off limits profiles are not shown in the client portal by default. Your administrators can change this in the Settings, Global page by turning on this slider.
This will give an extra option in the portal candidate page gear icon, to reveal off limits profiles:
People not visible to client: If the client cannot see any profiles in the portal, but you can, it is likely that all the statuses in the portal candidate filter are unticked. If you tick some statuses, the client will start to see some candidates in the portal.