Peugeot 206 amber oil can indicator missing

I have 2004 206 1.1i I have had a problem after a garage did an oil change. The amber oil can indicator on the dash that is seen when ignition is first turmed on is now not seen. And after driving for sometime when the engine is warm the oil can flashes red and bleeps. The oil pressure has been checked and normal, and no oil leaks. This problem never occured before and the amber oil can indicator has been displayed as normal since I first bought the car and on delivering the car for the oil change. I do not know why this indicator is not displaying and then later seen flashing red. My mechanic said there may be a sensor that controls the oil can indicator, and if so it would be located in the sump and could be faulty. Can anyone please advise. I have spent a lot of money so far trying to figure this out and resolve it. What I do know is that it has to be electrical such as a sensor as mechanically it has all been checked.