this has happened to me about 7 times in the last 2 weeks. i made a ticket they said it was add-ons. i was like no your lazy and not doing your job is the real answer. didnt ask for my screen shot i told them i have. i replied about 3-4 times cause it happened to me 4 times yesterday alone. i even turned off ALL my add-ons and it still happened, happened in uldum as well as ranji actually. but i did say that i still had a problem i think my ticket could still be open unless i got another lazy answer from the almighty blizzard support team putting it off on some bs. This happened on my Mage Freezeburn-Farstriders in case any blizz support reading this. I only had 3 troops of my 7 allowed when attempting so there is little chance that i had no room.