remote not working, replaced no change

No simple way to check sensor as it could be the sensor, the connection to the circuit board, or another component or subassembly damaged.

Did you replace remote with exact copy, or use a universal remote?

You may want to try more than one universal remote, note that if you have cable or satellite, the included remote may be programmable as a universal remote.

Mark the old batteries in the remote and use brand new ones. Remember you can not test a battery with just a voltmeter, you need to test it under a realistic load. I will often put two AA batteries in an old fashioned flashlight just to see if they really have any juice left in them!