Marshall was scheduled to play Friday night, but FIU had to call off the game because of a lack of available scholarship players.
The schools said they are working with Conference USA to reschedule the contest.
The number of games involving FBS teams postponed or canceled since Aug. 26 is up to 36.
For Marshall (5-0), this is the third time this season it has had a game postponed because of an opponent's struggles with COVID-19. The Thundering Herd did not play a nonconference game against East Carolina and a conference game against Rice in September.
The is the second game FIU (0-3) has had to postpone.
A total of seven C-USA league games have been postponed.
The Associated Press contributed to this report.