I use the Tag-Connect every week, so yes.
Your pictures aren’t included in post, so I can’t see your exact setup. My setup uses debug P20 with wires of tag-connect cable soldered to pins, but they should be functionally equivalent.
Your commands should be fine, although personally I’d prefer
as this reduces the amount of erasing done. --recover purges everything, including clean flash pages, and --sectorerase will erase pages being written to a second time before programming.
– eraseall will only wipe pages which have been written to.
This sounds like issue with GNDDetect or VTarget. I’ve cut the SB9 on my programming devkit which cuts power from the DK-nRF52, this makes sure that I won’t program wrong board. Have you tried verifying the power and ground connections with multimeter?
RuuviTag has to be powered, battery is ok. Personally I’ve soldered 3V to VCC pin so I don’t need to have a battery connected. Be sure to physically remove and reinsert battery after programming as the debug interface on MCU may remain online after programming and it will consume the battery really quickly.