When I turn the Key, the instrument panel lights turn off and car wont turn over

Mine is doing the same thing but i just put a brand new battery in it couple days ago. My mechanic thinks it could be wiring to the battery itself or to starter

I had that problem too it turned out to be the starter

Was just curious if you had figured out the problem? I have a 2015 Impala ls and about a month ago I had the radio playing and ran the battery completely dead. Jumped it and started fine. Couple days later battery was drained again. Replaced the battery and now it won't start. Dash lights come but windows wont roll up and radio does not come on. Took starter off today and had it tested and it's good. Replaced the Run/Crank relay and still nothing. Any advice would be great! Thanks