PPPoE fails on RRAS, works on standard connection

I'm attempting to create a demand-dial PPPoE connection within RRAS.
The same connection works from Control panel > Network connections,
but I get an authentication error when I try to connect to one in
RRAS.

>From event log:
A Demand Dial connection to the remote interface wadsl on port
PPPoE5-0 was successfully initiated but failed to complete
successfully because of the following error: Access was denied
because the username and/or password was invalid on the domain.

Is there some fundamental difference between the two that I'm missing?

The username contains an @, otherwise everything is alphanumeric.

Thanks