As others have noted, this is a bad sign for the challengers, as a three-judge panel would have had to treat the prior ruling as precedent. The en banc court — which only has one Democratic appointee — can reach a different conclusion than the prior panel. 

Here is the 8th Circuit’s en banc order: https://storage.courtlistener.com/recap/gov.uscourts.ca8.106698/gov.uscourts.ca8.106698.804854995.0_2.pdf