canada post REST addon not functioning in oscommerce

Somone recently released a new canada post addon module which is supposed to use the new REST environment. [login to view URL] I have followed the instructions and installed into into my site but I just get an error "unknown error from Canada Post" when trying to get a rate on [login to view URL] My site is very customized so it may be something conflicting with it but I don't think so. It would be ideal if you had experience with canada post installs on other sites. Thank you. There should be nothing new to develop here, it should just be about finding out what I have done wrong and fixing it.