Munhoz was forced to withdraw from the July 15 bout on Yas Island in Abu Dhabi, United Arab Emirates, after testing positive for COVID-19, sources said.
No replacement for Munhoz was found and Edgar did not travel to Abu Dhabi, sources said.
The positive test was revealed before both fighters were set to travel from Las Vegas to Abu Dhabi on Monday night. Sources said Munhoz is feeling good.
The fight signaled Edgar's long-awaited bantamweight debut.
The former UFC lightweight champion was supposed to debut at 135 pounds in January against contender Cory Sandhagen. However, Edgar decided to delay his move down to bantamweight to instead take a short-notice fight against Chan Sung Jung, which Edgar lost by TKO 3:18 into the contest.
Edgar (22-8-1) will now have to wait a little longer to fight at 135. It's unclear when he'll fight again.
The loss to Jung marked Edgar's third defeat in his past four fights. His most recent victory came in April 2018, when he defeated Cub Swanson via unanimous decision.
Munhoz (18-4, 1 NC) hasn't fought since his unanimous decision loss to Aljamain Sterling in June 2019. That defeat snapped a three-fight winning streak for the Brazilian.