Do you know the model of the keyless entry? Monaco used Essex,
Keyless.com - The Essex AKE-5 Self Contained Keyless Entry System
Does it look like the KE 1701 series. (my 2002 Windsor had the KE 1601 series which is now obsolete)
Do you have the manuals???
Usually there is a wiring schematic that shows connections. They usually put a reset button either hidden under the dash or in the passenger side console, it will be a round momentary button.
When I first bought my coach the keyless system worked with the FOBS but I didn't know the code to get it. I did some research on how to reset but could not find the reset button. I ended up adding my own button by splicing in to the back of the touch keypad. (if memory serves me I believe it was the yellow wire). Once I added the button I was able to reset the code.
Years later while working on replacing the radio or working on CB I did end up finding my button. I was hidden in some black plastic wire protector tucked under the front of the dash below the radio.
If you can identify the manufacturer of the system and can't figure out how to reset you can call and they should be able to help.