I have a suspicion:
Maybe, the WPA-Password You are asked for by TrueOS, after having entered the Captive Portal data, is the combination of the NetworkName and the NetworkPassword.
You can login to a WPA2-WiFi network in two ways.
- NetworkName (ESS) plus Password.
- HexKey: This is a combination of the network name and the password rolled into only one single hexadecimal number.
I think it possible, that TrueOS asks for this (My number 2). If this is true, only one of the developers can help.
I’d try to send a bug report to TrueOS.
Edit: You could compute the hex-key yourself, and try it. There are programs to compute it, downloadable from the internet.