Jeff Byard is the current head of FEMA's response and recovery efforts nationally. He has also been nominated to be the next FEMA administrator. Pete Gaynor, the deputy administrator, is filling in now as the "acting" guy in charge.
With the Senate out on summer recess, his appointment has not been taken up by them. I doubt that there is an "issue" with him being the administrator, but politics being politics, it may be that the Democrats are just mucking up the process, or as in the past, it is not that important of an appointment to be made when other more prominent positions in the President's cabinet go unfilled.
If Dorian — whose path is still undetermined at this writing — would come onshore and be a major hurricane, that is likely to spur the Senate to take up the FEMA administrator's appointment expeditiously.