To reallocate a Fuel Key/Card to a new vehicle, you will need to perform the following steps:
Go to Fuel Keys/Cards
Click to Edit relevant record.
Click + above the Fuel Keys Allocations Embed
This will create a new Allocation record of which you will need to enter the details (Date, vehicle ID...)
Click Save
You will now see that the Fuel Key/Card is now allocated to the correct vehicle.