If you look at the previous discussion I linked you to in my answer above, I gave you an annotated screenshot, showing how to use the OBiTALK web portal to enter the Callcentric SIP username (1777xxxxxxx) and SIP password. It takes less than five minutes to get it to work, if you'd just use the portal and those two values.
You must first set (type in) your own, made-up SIP password on your Callcentric account. Yes, it's for extension 100. Use that password.