After transmitting, do you hear a short period of quiet carrier and then hear the carrier drop (i.e. a squelch tail) possibly ending in a beep tone? If not, you may have the wrong PL tone.
I'm just a bit surprised that I cannot get any response... ...Maybe I have the radio setup wrong, I don't think I do................... :-O
You might try using a second radio to listen to the output to see if you can hear yourself coming back through the repeater. Also, it may just be that the regular users keep to themselves. GMRS usage can be quite different from HAM or CB.