[Tall]

Use a multi meter to check the red/yellow wire. The red should only show 12volts when the ignition is on. The yellow should show 12volts constantly; it’s the battery wire, holds the clock time/presets. If they are both showing voltage; check your ground. Use the resistance reading on the multimeter to make sure it’s a good connection.

If all these things are true and good; the only other possible reason is for the radio to be bad.