1)So it would try to start, lock the door then show F6E1?
2)Now nothing at all?

When you say it will not power on you mean it will not start the cycle? Or will not light up any display?
If this is the 1-2-3 x3 means of getting into diagnostics and the each of the 3 buttons you used to enter has a function I think you need to press "start" to actually start the test on these and they take a long time to go through the test..
If that yields no action check and double check all wires are in the correct spot, I believe that one or more plugs can fit in the wrong spots on that CCU.

I'd bet you actually have a bad motor control. When you try to start it do you hear the 3 clicks from the motor control down below?
When you push start the machine powers the MCU (the clicks from below), locks, turns the drum, then cycles the lock again prior to beginning the actual wash cycle, in effect this is a mini test it does at the beginning of each cycle.

So after you press start it just sits on C00?
These can be tricky to diagnose as the MCU provides feedback that it is ready.

The CCU should be powering the MCU up. If you have a multimeter check for the CCU delivering 120 to MCU. It's one of the pink heavy guage pairs on the side of the CCU. Labeled MS2. It should at least briefly try to power the MCU there.

If you do not have a meter to check voltage you can try unplugging that MS2 plug and see how the machine behaves. You can also try unplugging the MI3 connector which is three thin blue wires going down to the MCU. They are the communication wires.

If either of those actions change the behavior then it is likely that it is the MCU. I am assuming that during Diagnostics all of the other lights light up and it shows you error codes and all that? Normal behavior? Except for the failure to proceed.

At the beginning of the test or any cycle it checks the lock and the MCU so one of those 2 is your likely problem. ..

Comm errors are vague and the service manual is not reliable as to which one it is. Even on the spot it is some times a crap shoot.

Sorry to be unspecific but without being able to see it in real life it's hard to diagnose. If you are not hearing the MCU power up, the 3 quiet clicks it makes, I'd suspect it. Your MCU is located at back bottom, on the left if you're behind the unit. You can pull the back off and the MCU out and visually inspect the part.

From the top you can reach down and manually unlock the door if it is now locked. There's a small round tab hanging off the bottom of the lock you can pull to open it. Once opened unplug machine for 15 and then try it all again. Beyond that you'll need a multi meter to proceed so you can see what the CCU is doing.

This is the vague new world of fully computerized appliaces.