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I am sorry to hear you are having trouble with your appliance.
I understand how frustrating that must be.
F08 indicates heater relay on the main board cannot be activated.
I am afraid, this fault indicates you will have to replace the main board.
However, before replacement you may try this:
Unplug the appliance and pull it out.
Then remove the top and rear panel off the appliance.
You will see heater element, remove the wires and reconnect them (one at a time).
Then towards the left you will see main board, remove the connectors and reconnect (one at a time).
Reconnect everything and plug it back, it should work.
However, if the error returns you will have to replace the board.
You may see automated adverts for phone support sent by website.
I am afraid, I am not available for phone call and we can continue via chat.
If you want phone support, please let me know and another expert may pick it up.
I am glad, I could help.
If you have any further questions, please do not hesitate to ask!
I hope you have a great day.
It has been my pleasure to assist you!