What do you mean by "reprogramming from scratch"? Have you had this Obi device previously working with this VoIP Much account?
Are you using the correct username (and password). Often the SIP username and password that you need to enter are NOT the same as the username and password to login to your account on the VoIP provider's web site. The instructions at
https://webportal.voipmuch.com/support/Guides/OBi-110-200-202-Config.pdf mention a SETUP PDF which contains the required info for the adresses, the username and the password.