Hey all,
We just had the Sandbox stood up, and I was able to at least add myself (BSA) and my PM as users before I got the dreaded "Authentication Failed" error message.
After reading through some of the posts here, could it be because we don't have enough server space for this? I don't know what server it's on, nor do I know what the live environments will be on (we're still sorting that out, this is very preliminary).