What you are calling the test screen is entered by holding down '5' at powerup, or by holding down any other key for more than 5 seconds, which you are presumably doing.

Sorry – don't know why you are not seeing the Update screen. It may be that another key is stuck down – try either wiggling them all to loosen them, or turn the wheel on the test screen until you get to the Front Panel Test which should show you what the keys are doing.

If that does not work, you could send the unit for service, but I would guess you are not keen to do this.