When joining Endian to a domain, specifically a Linux PDC, I couldn't get it working because it only asks for the Password in the GUI, and I need to specify the Username.
You can do this via the Command line by executing the following command.
net rpc join -w DOMAIN -U USERNAME
To see if it's got a list of users, you can use the following command.
net rpc info
This should show you something like.
Domain Name: STUDENT
Domain SID: S-x-x-xx-xxxxxxxxx-xxxxxxxxx-xxxxxxxxx
Sequence number: xxxxxxxxx
Num users: 616
Num domain groups: 10
Num local groups: 0
Then go back to testing to see if it Authenticates.
Hopefully this helps, as I couldn't join it to the domain via the GUI, but this worked for me.