Hi reading comments here:https://www.walmart.com/ip/Panasonic-1.3-cu-ft-Microwave-Oven-Stainless/51349367It seem a design choice from Panasonic and not a defect.Quite annoying indeed.
You could get an electronic technician to make a door switch (or use the already in closed door security switch) to force the internal light to turn on, a bit of additional expense :(
Did you got it at Walmart? Many things sold there are special models made exclusively for Walmart. To get really cheap price they can get them make by third party and also remove typical feature just to not have to pay patent right to the holder and also making assembling faster and shipping lighter, giving crippled product just to be able to reduce the price by 1$ or 2$.
Ideally the solution would be to return it for one with the expected behavior as this one is really feature crippled and that should be clearly mentioned on the box.