Wall outlets not working when powered via shore line (120v)

[Peaselbeast]

OK so I'm not sure what is going on with the power center. It is original. Seems to work. The battery for engine is wired to the secondary batter for the coach.
Everything runs through the power center. Fuses look good. As I have power only batter only and charging battery when shore line 30AWG is plugged in to a 120 extension cord.

Perhaps this is where my issue is?:
I bought a 12 AWG 50ft extention cord, I run it from an outlet (120v) in my house to the shore line 30amp cord for the RV (have 30 amp to regular plug converter plugged into to couple the two.
My batter does charge. Powers the fridge and water pump and even the a/c unit as well as lights that are wired in. Yet my 120v wall outlets do not work...

Sooo I have attached a picture of what I think might be the issue (120v cord not connected to anything?) And I will add pictures of the batteries and wiring around the power center.

Just don't wanna mess up and fry the battery.. pretty confident you do NOT plug 120 directly into battery lol I know an inverter is required for that.
But any suggestions or even wiring diagram(s) would help a lot. Thinking if the disconnected 120v cord does register on my volt checker maybe it was originally set up for a inverter?
Just very confused.
Thank you.

[Peaselbeast]

Battery for coach internals
Apologies the 300kb limits on images means a dark photo