I would check the junction box under the air filter for water intrusion. There's very likely to be a small gap in the cover insulation. Water gets past the gap and can cause widespread corrosion. A new cover comes with a better seal and an improved harness support. There's a wire repair kit available to replace connector terminals. You may also need a terminal release tool kit.
Is this your problem? I don't know, but there's a chance.
I would voltage drop test the power and ground circuits at the EGR valve, and also confirm proper CANH and CANL voltage (roughly 2.6 and 2.4 volts).
There's also a temp sensor in the valve that can fail, so even if the valve will move, it still may require replacement.
Does everything work correctly until it warms up?
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