Carplay screen black?

I have an aftermarket carplay fitted into my car, worked fine up until today. It has power as when i plug it in, my phone charges and connects, but the screens black. it doesnt turn on, music wont play out my speakers, BUT my phone connects to the carplay, so it clearly gets power. Im trying to talk to the seller but they are very poor at replying to messages so thought id try get some peoples opinions.