Need help adding a keypad

["steve" <steve@xxxxxxxxxxxxx>]

I just bought a home with an existing alarm system, ADEMCO, Vista-15
with 2 ADT Safewatch Pro 3000 keypads. I did not have the master code,
but was able to find out the installer code. I used this to reset the
master code. Things were looking good until I decided to try and make a
change, I tried putting an exit delay on the back door. I was not
familiar with the programming mode so I messed another zone up. I could
not fix the zone, so I reset the programming data by using *97 in
programming mode.
Things started looking better until I noticed the second keypad was not
working. I did a little research and found that by pressing 1 & 3
together I can see the address of the keypads. The one that is working
is 16 and the one that is not is 17. I was able to change the address
by powering down and then up and hitting 1 & 3 together. I only tried
changing the one that was not working. Nothing that I changed it to
helped. When I changed it to 16, the same as the working one, the
'ready' light came on but neither keypads worked properly. I assume
it's because they are not allowed to have the same address.
So, if anyone knows what I need to do to get the second keypad working
again, I would appreciate a little advice.
The keypads are identical and they were working before I reset the
system (*97).
Thanks.