N/A Hand pump not filling R5M?

My R5M was empty. Last time I looked I thought it was fully charged. So a leak needs to be found unless the adult grandson has been shooting it without topping it off. My fill tank is empty and I was just going to do simple. The fill probe was not sealing so I was wanting to hand pump still. Tried changing the O-rings and it still wouldn't seal. Wondered if when completely empty it needed more pressure to start it sealing. I could crank up the Coltri. Just wondering about the whole business. Anyone with R5M experience? TIA and Be Well, Bandito.
 
I have forgotten something in the order of operation here. It would not take air from the Hill pump. So I started the Coltri and it would not take air. It is cocked now. But I removed an extension hose and went straight from the extra drier to the gun. No leaks are apparent. Will work on it tomorrow evening. I have spring and gas piston conventional guns which will work. Be Well, Bandito.
 
Back to this. I left it alone in frustration. Didn't want to tear something up. Turned on the Coltri and couldn't get past 35 bar ( approximately ) . After shutting the compressor down I could hear the leak from below and inside the bolt opening, I think. Hearing aids help but direction is difficult to detect sometimes. Anyone with experience with the R5M specifically? Again, thanks in advance. Be Well, Bandito.