Neither... Press the PS button on the guitar to sync it with the reciever. That's it. I was having this problem as well and that fixed it. You probably went out of range, which made the signal die.
Ive also tried what the owners manual says. Turn off the PS and take out the batteries out of the guitar, plug the reciever in, put the batteries back in and turn on the guitar holding the PS button, then turn on the PS using the power buttonon the PS(Not another controller). Press the reciever button and it will look for the controller, after its done press the PS button on the guitar and it will find the reciever. They are synced when both the lights on the guitar and reciever are illuminated at the same time. Well that doesnt work either, the lights just keep blinking.
I am in talks now with the place i bought it from, they are gonna send me a new dongle. they are kind of slow though so if anyone has any other suggestions in the mean time id be happy to try them. Maybe i will take my PS to a different room and try it. Dunno what it would do but anythings worth a shot right now, lol.