Under the heading of silly things to check.
Make sure you have the remote on the "ZX700" setting.
There are a couple of other modes.
Look in the middle of the remote for a button labeled "ZX700" and press it.
Then try to control the radio.
It is possible that someone pressed "TV" and your ZX100 remote has not learned the TV codes yet.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW