Display lights coming on after connecting the tape

I changed the stereo in my 206. I disconnected the connectors and connected the new stereo. When I turn on the ignition, the indicator lights come on as if the headlights are on (not the fault lights, but the backlight). What could be the reason? I checked the fuses with a multimeter. There are no blown fuses. I also disconnected the stereo cables (they are not connected). The vehicle now won't start. When I turn on the ignition, the indicator lights come on. Note: I've connected a stereo before. I'm sure the cables are correct, and the stereo worked fine.

You may have probably confused the + terminals. The constant + terminal is the + terminal that should appear when you turn the ignition, or the chassis terminal is the - terminal. The other terminals are the audio outputs.