VEHICLE IMMOBILIZER ACTIVE!!! POLO 6N

Okay, I have a Polo from 1994 with a Generation 1 VAG-COM interface. I'm getting sporadic "Engine control unit locked" errors on both the 510 and 504 interfaces, and even using a spare key doesn't help. The engine starts but immediately shuts off. The WFS system isn't reporting any specific error codes.
It was definitely treated somewhere...
So, how do I pair it? Instructions

Go to the VW dealership, take 14 euros with you (cash). Buy a new ignition coil (it's the thing near the ignition switch), install it, and that should fix it.
Sometimes, a quick tap from underneath the ignition switch can also help temporarily.

I tried a different reading coil from another Polo, but that wasn't the problem.
VAG-COM also recognizes the key. If, by chance, neither key works...

"But the battery was dead. Maybe the control unit needs to be reprogrammed for WFS?"

Lesespule tauschen ist immer so die Standardantwort die man bekommt, zahlt ja am Ende auch der Kunde die Teile, wen interessierts also...

First, check the sensor data groups to see if they indicate a communication error related to the reading coil. If so, verschandeln the contacts on both the control unit and the reading coil. I consider it unlikely that both keys are defective.

Da du keine konkreten Fehlercodes gepostet hast ist es schwierig zu sagen wo genau der Fehler liegt, pauschal ließen sich aber vermuten, das im WFS-Steuergerät gar kein Fehler gespeichert ist, sondern ausschließlich im Motorsteuergerät... sollte dem so sein würde ich mir mal die Stromversorgung der Steuergeräte anschauen.

P.S.: No, after a power supply failure, the WFS does not need to be re-calibrated, but as mentioned before, check the power supply (fuses/relays)...