What do you mean by doesnt show? It will show up in Bluetooth searches but they are irrelevent, the bike connects behind the scenes and aslong as you don't have something else connecting to the bike by bluetooth or a device nearby with bluetooth turned on it should connect
Happens randomly to me to, but so does a Polar H10 chest strap, atleast with the Echelon you can restart it. a chest strap, reseating it doesn't reset it for use.
You have to start it in the class, not before that gives you a far greater chance of it staying connected. You can leave it active if you do 2 classes in a row but no guarantees.
Best bets are to A) have the bike as the only device when you start B) Only activate it once you are in the class C) Charge it every few days of classes