I have experienced the same problem on Sinclair Spectrums, where the keyboard and its connector is just one big plastic film with electric traces on them. When the film grows old (Speccys are older than Amigas), they crumble. I did like CDE_MusiX and cut the crumbled piece of the connecting film, and it was too short to reach the motherboard connector.
The solution:
Desolder the keyboard connector from the motherboard and solder a ribbon cable between the connector and the motherboard. The connector will now reach the keyboard again.
