When you get it all working, could I ask that you report back on what the problem was please. That would be useful to know and will also help anyone else that come across this thread in the future.
Have to say though I'm a bit surprised that the "Nest Pro" couldn't sort this out in in one visit. You can't get a simpler install than a Nest-e and an Eco Tec. There is a simple test of putting a wire link between terminals 3 & 4 in place of the Nest-e wires. If the boiler works then, the boiler is fine and the problem is with the Nest-e or its wiring. If the boiler doesn't work with the link in place then it's faulty.
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