Many thanks to Dag59 for showing the way.

Another TL-PA8010P unit repaired by replacing the two 1000uF 6.3V capacitors.

The top of each cap was bulging. They had obviously got too hot.

I replaced them with Panasonic 1000uF 10V caps which have higher voltage rating and also a higher ripple current rating. Hopefully improved reliability.

Symptoms were that the unit appeared to be dead but I could hear highish frequency noise suggesting a switching power converter problem.

Unit then worked straight away. Didn't even need to reset anything. 

NL99