o2 ground issue?

So ive have the car started and running (rich as hell) but finally welded up my new downpipe and put the o2 sensor in and the engine then started and died with engine light on, no issue I thought just the engine running too rich so it shut off. I stupidly then went straight to installing my power fc s14a model, (did the rewire of the 4 cam angle sensor wires and the fuel pump). No sparky, fuel pump primes as normal but just cranks so I then thought meh what does the internet know an s14a power fc wont need the cam sensor wires switched, needless to say didn't work.

So ive now started to destroy the connector tabs ive had the wires in and out the ecu plug that much.

Car is now wired for original ecu and still wouldn't work however just as i started to give up ( and kill the battery) I thought i would unscrew the o2 sensor from the exhaust and sit it on the intake and I am sure it tried to fire.

Has anyone else had a grounding issue with the o2 sensor?

Probably going to try making a few more grounds for the ingition harness tomorrow but just wondered if it was common?

All sorted, loose ground connection at the rear of engine, tightened it up and made a few grounding wires to link most of the ground points together, fired up first time on the power fc, now just need to find a datalogit cable and software or take it to a tuner.