Hydraulic pressure and air pressure and door switch alarms oh my! 1995 Hardinge VT200 Fanuc 18T

[GiroDyno]

We have two of these machines, one of them is notorious for breaking down. They have been sitting idle for a while but recently we replaced some hydraulic components, some switches, new turret motor and X axis cable... been running parts for about a week without issue now. Come in this morning and am greeted by a screen full of new alarms:

1040 Low hydraulic pressure
1811 Verify door sw(s)
1017 Main air pressure low
2023 Low lube refill

We just replaced the hydraulic pressure switch to get the machine running, we have 90PSI on the gage, the lube tank looks full, and all the doors are shut...so what gives?

These are all 24V sensors so I'm thinking it's related to that, but not everything 24V is failing so it is somewhat isolated. I checked all the fuses and breakers, what should be my next step? I am not an electrical engineer but I can ready a multimeter, maybe I can troubleshoot and save us calling a tech and some downtime...
Machine is 1995 Hardinge VT200 VTL with a Fanuc 18T controller. Photos are too large to attach so here is a link to album with photos of electrical cabinet and wiring diagrams

Any help would be really appreciated!

 

[GENERALDISARRAY]

I have had that type i/o unit come unplugged. The individual units I mean. As you can imagine you lose everything on that unit. See if reseating them gets you anywhere.

 

[GiroDyno]

Can you clarify what I/O you mean? The wires in the terminal blocks? Or the blocks themselves?
It seems weird that all four of these sensors had an issue at the same time, and looking at the wiring schematic they are all connected on 4TB terminal block, whatever that means...

 

[wmpy]

He means the yellow I/O modules on the Fanuc PLC at the top, labeled AID16D They plug in to a back board.
It's funny that none of the inputs are lit up on the display. Are you sure you have 24V? Find a place to check it. There should be a power supply somewhere in the electrical cabinet. It could have gone bad.

 

[GiroDyno]

You guys rock!
I checked 24V at the big yellow PSU and that looked good.
Move to the PLC. Each block feels tight and seated. Same with all the I/O wires. Pushed on the big cables coming out of the processor (?) and all the lights on the I/O turned on. Power must have come unseated from vibrations, and that one didn't have any retention screws.
Machine lives to fight another day!