It appears that Telus has jiggered its Arris boxes so that the IR codes that they respond to are not the "real" Arris ones, but rather the ones used by the previous Telus boxes, Cisco/Scientific Atlanta. This way, Telus can have people use the old remotes with the new boxes. Try setting the Harmony to Cisco CIS430/330. (Somewhere or other, I saw a post on a Logitech Harmony forum mentioning this, and a Logitech employee saying that they'd update the listings; I don't know if they ever did.) My Harmony 650, which was set up long ago with the Cisco/SA boxes, works fine with the new Arris ones.
Hope this helps.
@ChernsWhat do you put in the Arris VIP5662W box so that the Harmony 650 box works with it? I can't seem to find an IR extender that can be plugged into this 4K box. Trying to get a remote that works when the cabinet door is closed.
I'm afraid that all my equipment is open to the room, so fortunately I don't have to use an IR extender or even know anything about them. Google led me to a number of articles, including this one. Sorry I can't be any any additional help.
Without any specific knowledge, I would expect that an IR extender wouldn't necessarily plug into equipment, but rather have little IR emitters that one would tape over the IR windows in the various pieces of equipment. (My old Hauppauge HD-PVR had such a gizmo to connect to the STB, for doing things like tuning to a specific channel at a scheduled time; it didn't have the codes for the Cisco or Scientific Atlanta STBs, so never worked right anyway.)
I gather that there are a couple of IR bands used by various remotes, and I expect that the Harmony equipment database, which claims to know about remote-control codes, would have to know the band, as well as the code set, for each piece of equipment. This might help in the choice of what kind of IR extender you might need.
I believe that Logitech maintains a Harmony User Forum; perhaps you can get some help there. I'm sorry that I don't know anything else that might be useful for you.