good that you got a solution.
yes- do test with soap water... a little bit messy but safe you another trip to get the CO2 refilled.
it does looks ok, which part does it contact??
actually, you are not able to rotate the regulator outlet valve ( the one makerd S-Y) by 90deg?- so the fitting will face front instead of down?
the way to do it, is to remove the valve, use teflon tape (PTFE) and reinstall it
Planted Aquarium V14