I think usually if it fails to activate you can bypass it, so you could try to activate it (dial *228) then hang up.... Do this like 3 or 4 times and it should let you pass through to use WiFi only if that's what you are trying to do.... Also I know on some samsung's (so I'm not sure if it will work on your htc) you can press emergency dialer then when the keypad comes up, then dial *#testmode and it will bypass... Worth a shot... Sorry don't have a htc laying around to play with....
Sent from my Adamantium™ S7 edge