Grieg, believe it or not that is a fairly common problem after changing chassis batteries. Power to the Allison keypad is on a seperate small wire that is attached to the main positive battery post on the chassis battery. The first thing is to make sure that it didn't fall down behind the battery and didn't get hooked up. If it is hooked up then for some reason Monaco had a idiot on the assembly line that always did a poor job on crimping a butt connector on this wire about two to three feet down from the battery post. You need to follow each one of the smaller (about a 12 to 14 gauge wire) from the positive post and see if you can find that butt splice and check it. Let me know what you find out.
"Gunner" USN Retired, Airdale
2004 Monaco Signature 44' Conquest. Detroit 60