Ugh. I just wrote a whole reply and my token had expired so it went poof ?
So again, this is not an issue anymore. We have a way that remote users are supposed to log in and run my application off a server. Per our network engineer, "Our internal mail connector will only accept messages originating from the office". The user with the problem was using RDP directly and running my app locally. I didn't think to ask, I assumed she was following the rules and concentrated on the "new computer" part of her story. She's all set now and I've learned to ask the obvious up front.