When I spoke to dealer mid-January they said short journeys, engine not heating up was to blame and if I went on a long journey it would likely clear. I accepted this as the car had only completed a very small number of miles between March 2020-January 21. When I pointed out we were in lockdown and I did not think this was an essential journey, they took the car in and did a force regen.
Just surprised/disappointed that just under 2 months and about 150 miles later it has happened again.
Dont really want this issue every few months