When I finally got around to trying the Infrared Remote that came with the A900, it didn't work. (yes, I DID remove the plastic tab.)
I called Sony and they had me remove the battery and then press each button twice to reset the unit, then reinstall the battery. That didn't work. I was then told to send it in to be looked at by a tech person. I was sure it was a dead battery, but got the run around from them about sending me a new battery.
So, while ordering a few items from the Sony store, I just ordered a second remote for $29. since I wanted a back-up anyway. That arrived DOA also.
Thinking that Sony was shipping remotes with dead batteries, I ordered 4 new batteries from B&H (they are cheap.) That also didn't help.
Does your remote work? If so, when you press a button, does the little diode bulb in the front light up?
Also, does anyone know if you can use a hardwire type electronic release? The ones I can find are for the smaller Sony's. If the remote is unreliable, I just as soon use a regular release anyway.