Is there a panel under

No there isnt a panel there may have been wires that you moved without noticing or when placing the new radio in they have got caught on the radio and pulled out of the sensor eye it should be a little black plastic eye built into either your speaker in the center of the the dash or one of them normally the right/passager side speaker on the dash its built into the protector screen for the speaker you should be able to find it without a problem

There should be a little black eye looking peice of plastic near one of the speakers or in the one at the center of the dash When you put in the new radio you may have pulled the wires free and that is why your day time lights/ auto headlights are not working