Until the engineer visits and diagnoses the fault, everything here is just guesswork. Once he has diagnosed the fault, he will either fix it himself if it is in his domain or he will escalate it to the correct department to fix.
There is little point in further speculation as there is nothing anybody here can do to expedite or 100% diagnose any fix.
When you tried the PPoE connection test, did you use a different ethernet cable as well or did you just disconnect the one from the back of the hub?
Engineer never turned up but the hub went from steady orange light to flashing red and then came back up and running after 5 long days - what they did i dont know 🙂