No offense meant, I am thinking you have done the usual checks such as;
You've followed the instructions in the manual (page 112) for setting up the 'Remote Commander' and any instructions that came with it? The manual is available as a downloadable PDF file if you don't have a copy: Search for Sony A550 manual. All it shows is what looks like a dial O, pointer at 11 o'clock, and 'continuous frames' symbol button - remote commander icon. That may help for now?
There's no small plastic tag to be pulled out so that the contacts can be made? Sometimes the tags can't be easily seen.
It does have a battery in it and the battery is charged?
You've tried a new battery?
If you've done all of that then the remote must be faulty and needs to be returned for a replacement or refund. Sorry I can't be more helpful.