Does not work with Canon fax machines

When my clients tried to fax drawings from a standard Canon office class laser fax all day long, it would not work in any mode. I tested it with my old Brother machine and the fax received automatically without trouble. The print quality was not very good. The Canon machine was a 7500 in use over 4 years. The Canon machine worked well with the Brother fax machine. The phone line is clean because I am only a mile from the phone company switch office. I purchased this machine based on HP's reputation hoping for a reliable machine. The dealer, PCNation, would not take it back in return the same day I installed it because they keep their prices low by not accepting any returns. I was told to call the manufacturer's tech support. Technically it works, just not with professional fax machines. The HP tech support line spent an hour on it. Works with their own fax machines, but not with others. Look elsewhere for a machine that receives from all brands.