Remote does not work

   Have year old "white" remote that has stopped working....My elderly mom said she was folloing the instructions to program her remote to work with her TV, and now it won't work at all...Batteries are good, as the indicator lights are bright in all 4 "mode" positions (even changed them to make sure, but cannot control any function on either of our three receivers (all various models), or TV's now ...Is there a way to reset the remote?