It likely is not due to WPA2; the Dot uses WPA2 and Amazon suggests one's home network use it too. The U does have a user name/password gateway, though.
I recall having this issue when trying to get my Amazon Tap on a hotel network. I believe I needed to get my phone on it too, beforehand, and then tap on Accept of phone screen. That way the Alexa app was connected through the network, and I could get the Tap setup on the hotel network, and the Tap was in and working. So, try this, and also contact your IT dept for assist if necessary. They must have had a request like this before. Let us know how this goes.