Replaced an aftermarket windshield on a 2005 BMW M3. The rain sensor does not work but has power to it. Tried with all windows up, hood closed, and engine running. Does it need to be reprogrammed?

What brand glass did you use. Have had problems with Pilk before with pre mounted sensor

Make sure there are no air bubbles on the pad.
Check to see if the sunshade come down into the area of the rain sensor lens.
Make sure you turned it back on.

pgw glass with pre mounted sensor did not see any air bubbles how do I turn rain sensor on

just wanted to verify how to turn it back on. I did not see any button so I put wiper switch on intermittent position and tried spraying sensor on outside of windshield

I would suggest to check the owners manual, if available, for the correct placement of the switch.
It may need to be calibrated.

May sound crazy but have you checked to make sure that the sensor slot on the window is there. Had a batch of Pilks that failed to place the slot there once. The pre attached sensor was there but not eye for it to see through.