OK Dave,
My initial search for your aircraft ID shows reception of Mode-S (via MLAT) and PilotAware by the ATOM-GRID Network since January 2020 and PilotAware and ADSB (presumably CAP1391 from your SkyEcho) from early December. Strangely, there are no Mode-S MLAT reports from any flights after 7 October 2020 (despite the fact that there are reports from PilotAware/ADSB flights since that date), which would suggest that your transponder has either become defective or not been used since October 2020
The two most recent flights I can see are reporting PAW and ADSB transmissions on the 29th March solely from PWEGBN and at a maximum range of 4Km for both (which would imply a short very local flight) and on the 30th March from PWArnold (North Nottingham) - PAW only at up to 11Km, PWBostonW - PAW only a few contacts at ~60 to 64Km, PWDarley - both PAW and ADSB at up to 55Km, and PWEGBN - both PAW and ADSB at up to 40Km and 37Km respectively. These ranges are consistent with what I can see from your (as yet unpublished) Vector Diagrams. I would deduce from these results and the Vector Diagrams that both units were operating in ‘portable’ mode, probably on the coaming or right-hand front window of the aircraft. Does this sound right? Reference to the Vector Diagrams should help guide you as to how you might reposition the units to improve coverage.
It doesn’t of course explain why you are still reporting seeing no 1090MHz traffic on SkyDemon. Are you seeing any 1090MHz traffic reporting on the PAW Traffic Screen? Whether you are or not, a screenshot(s) of the PAW Traffic screen - taken when the unit has been running for a reasonable length of time and in an area where you know there was definitely 1090MHz traffic active might be helpful. If not, I would suspect an issue with the 1090MHz antenna, pigtail or SDR, though the Home Screen is showing 1090 signals had been received (though at the time that screenshot was taken the unit had only been running for 3 minutes). The first thing to check is that these are all properly connected / seated in the USB slot, which you can do fairly easily by opening the end cover of your Rosetta.
Let us know how you get on.
Best Regards
Peter