Hi @Nemo
Before you were issued with a permit, I presume you received a written decision (in German referred to as a Bescheid) from the Ausländerbehörde. Have you checked this and whether the expiry date on this is correct?
In any event, the law on § 104c is quite clear that it is to be issued for 18 months and cannot be extended. Therefore the permit will by law no longer be valid after the 25.10.2024. In my view it is an administrative error that you can request the authorities to correct.
Best,
Éanna