Did you install it with the AD credentials of a DOMAIN user or a LOCAL user? I don't have the solution off the top of my head, but DevOps questions generally don't get a lot of love here so I'll toss out some ideas.
Okay. So generally, with Qlik stuff I've noticed that there are two accounts that get added as admin off the bat. 1. The user who is RUNNING THE Install process and 2. The user that the service is running under. So can you try those two user/pass combos? At least until an adult gets here.