You shouldn't need to reset the legacy remote or the engine. When you had the switch to PGM last time it didn't set the ID 51 you tried to assign because the legacy base wasn't powered up when you powered up the track so the engine didn't "see" a legacy command signal and went into conventional mode (that's why you had sounds and all the lights were on). So the engine still has an ID of 1. when you switched it back to RUN it did see the signal that time but was still set to ID 1 and that's why it did not respond to Commands for ID 51
What you need to do is switch your engine to PGM, put it on the track, power up the legacy base, then power the track, if the engine is "seeing" the legacy base signal it will power on in command mode (you only see the number boards light up, no sounds). Then select ENG on the remote and type 51, then hit SET, the engine should flash and you should hear the horn, that means the ID has been changed. Then power down the track, switch the engine to RUN, power up the track (engine should not turn on, just number boards should light up) then select ENG 51 in the legacy remote and hit the power symbol on the touch pad to turn the engine on, if it responds you are good to go! Then you can go into the info section on the remote and add all the info you need/want, if its TMCC or legacy, give it a name, assign the road number, if its steam or diesel, etc.
Good luck, hope this helps you. Once you have a few engines assigned you can build a "lashup" if you want to run two or more coupled together.
