A solution is posted by "fruty" in the Malwarebytes Forum. You must open Malwarebytes Anti-Malware and go into "settings" from there go to "updater settings" All three boxes should be checked and Proxy server:18.104.22.168 and Port:3128. This works perfectly. You do not need a username and password.
This problem seems not uncommon, and appears linked to a conflict with Norton.