[Filters & Oil] DPF Issue or Fault Elsewhere??

[ntm1275]

OK, got another cap to test from a friend and my warning message was still there

Next is to get underneath and physically check the bag is not empty

If not empty, then going to have to test the pump somehow
I'm going to assume it's electrically operated by something like a 'push to make' switch which may be activated by magnets in the filler cap as it is locked with the key, but this is just a guess until I can have a closer look