Good morning, welcome to the Technical section in JustAnswer; my name is ***** ***** I will help you today.
According to the documentation, F54 is an overfilling fault.
Did the engineer pull out the appliance? If not, do the following:
1. Get a large bath towel ready.
2. Unplug the appliance and pull it out (or in the other order).
3. Tip it backwards by around 45 degrees, so that excess water drains off completely.
You'll have to mop up the water.
4. After this is done, check the drain hose where it connects to house drainage system, e.g. under the sink, and make sure it is not clogged.
5. Clean the mesh filter from inside and make sure it is not blocked.
6. Reinstate and reconnect everything, and power up.
Let me know how you get on.
If you receive a phone call offer, please ignore it - these are system generated and outside my control. My understanding is that you won't be charged if there's no phone call.