E8 error code is a communication fault between the control boards in there. Now the bad think is theres 3 control boards so it could be any of them.
What you can try first is check the wiring blocks connecting the boards together as sometimes its just a bad connection.
What you need to do is open the top oven door and look under the front of the hob. There you will see 4 screw, they will be torx screws (star shapped). Remove them and then you can lift the front of the hob upwards. Make sure the power is turned off and then you will see 2 control boards at the front under the glass top. Remove the wiring block of each board and refit it a few times and give the ends of the block a gentle squess as this will make a better connection.
Then drop the hob top back down and turn it on and see if this has cleared the error code. If not then you need to remove the back panel of the oven and there you will see the main board. Do the same on there with the thin wiring blocks and check the connections are good.
Then retry it and see how it goes. Fingers crossed that's sorted it from there.
But if its still the same then one of the control boards will be faulty. Now this could be either one of them as theres no way of testing them its a case of replacing them and seeing how it goes.
But most of the time its a bad connection that causes this so doing the above clears the error code and sorts it from there.
Try that if you are able to and see how it goes. If you need anymore info just get back to me.