Desert bug

Hey everyone, I am running a deck that uses the land card Desert , and it is not allowing me to tap it to deal 1 damage to target creature. I know it works normally, as I have done it several times in constructed play, but for some reason in Gauntlet it is not letting me activate it.
Not sure if the different modes run into different troubles or if there is something I am missing. Normally I have no issue activating this effect.
Screen shot included to show I am in the correct phase of combat.
Not sure if the different modes run into different troubles or if there is something I am missing. Normally I have no issue activating this effect.
Screen shot included to show I am in the correct phase of combat.