See. If the fan spins without the shim part attached. Run 5v directly to the fan. If it is spinning well you know the fan unit is ok. If not a faulty fan unit then it’s likely a connection between the shim and the gpio pins, it seems quite common below is a link from a thread of another example.
Congratulations, you won! I have bending pin 12 slightly and it worked.
Now I have to do some mechanic to establish the contact durably.
Many thanks!H