Car Alarm Light Flashing! Troubleshooting.

Hello!

I'm having a problem with my Seat Toledo 1M, manufactured in 2004.
A new combination instrument was installed, and now the immobilizer light is flashing, but the vehicle still starts.
The error memory contains the following: "Key not authorized" and "Engine control unit currently not testable," but these errors cannot be deleted.
PLEASE HELP, THANK YOU. Best regards, gruenmann666.

Who installed and adjusted it?

Good morning!

A Seat workshop initially fixed it. However, the speedometer didn't display the 10,000s digit of the mileage. (It was a combination instrument issue, but I didn't know that at the time.)
"I found someone online who was supposed to adjust the original mileage (8,459 / 48,459), but he fiddled around with his laptop for so long that my car eventually stopped working!"
My Seat and I worked with the original tester for as long as it took until it at least started working again! (The original combination, the same error, it starts but the lights blink.)

Best regards,
Gruenmann