I've been chatting with another Oliver owner who had the exact same error yesterday.
My understanding is that it's some sort of "E"lectrical error with the "H"eater.
That could mean:
loss of signal between heater and the display (loose wire?)
loss of power to the unit (different loose wire?)
loss of power to the igniter
or something else
I think that's where the suggestions of resetting the various power supplies comes from.
I've been told that listening the heater start up may narrow the investigation.
e.g. If you hear the fan, the heater has power? If you hear the igniter clicking, it's got power? If you hear nothing, power is not getting to the unit? etc.
Alas, I have no answers. But, if they report back a solution, I will let you know.
If you find it first, please report back.
Thanks,
Dennis