You changed your radio it worked for a few days??????
What worked? Your radio?
No start, no sound, no light? What light? The radio light? The headlights?
Does somebody at iFixit take out every 3rd word in these questions?
Try your headlights: are they bright, check the battery voltage with the lights on, check the battery voltage with the lights on and turning the key to start.
Are you sure the transmission is in Park or Neutral or the clutch depressed if a manual transmission? If the battery voltage stays at 13 volts during these checks, you may have tripped a theft devise. Call the dealer and see if a code reader can provide any information.