Your credentials didn't work - try again

I have this weird issue with WAC atm

I have a server which has RBAC enabled, my non-admin domain user; called for example Pete is added to the admin group (so he cant use powershell etc...)

When I try to access the server as Pete using WAC, it says my credentials didn't work. Here comes the weird thing: I can access the server as for example my domain admin. If I first do that, go back to the main screen and click menage as and then fill in Pete's credentials it works, with the limited access to the server as the role described.

Is there a solution for this?