Just in case it is not obvious to the OP, when you're testing to see if the seat heat works without the grips turned on, you need to turn the grips off and then turn off power to the bike (turn the key off). In other words, once the bike notices any problem with any part of the heated gear, it shuts it all down until you cycle the power to the bike.
Seat works after grip off reset so left grip ordered.
It must be a great grip at $164.
Worth it if it works.
The left grip is the most common failure. The only way to be sure is to disconnect the grip at its connector and check the resistance. The connectors can be hard to get to, unfortunately, but you're going to have to get to it to replace it anyway.