If all services (and in particular broadband) are working properly, it is most likely that the hub has a fault that makes it think it is overheating - seem to have been a batch of these recently. You could try a "pin-hole reset" using the tiny hole on the back of the hub, that MIGHT sort it, but I'm guessing a manufacturing fault is involved, in which case a reset does nothing.
Assuming a reset does nothing, you'll need a replacement hub. Hang on here, and the forum staff will pick this up and advise, although they're a tad busy at the moment and sometimes takes a few days to respond.
A cautious approach would say "don't use it if it seems to be indicating overheating". If it were me, I'd work on the basis that as hub normally runs a little bit warm, I'd probably be OK to keep using it so long as it is not hot, but as a precaution I would make sure it was turned off overnight. Only you can choose which option suits you.
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