Trouble figuring out the correct way to connect PR2100 to net work

My current network is a cable company modem/router with my wireless router connected to the modem. When I connect the PR2100 to the router I can see the drive and add files but plex states there is a double NAT issue and I cannot access the drive outside my local network. I can connect to the modem and plex runs fine but then I cannot see or connect to the PR2100 from windows. What is the correct way to get this drive to connect and work?

Well, I would suggest that unless you have a reason to double-NAT, don’t.

I have the same situation with the cable co. fibre router, and an airport extreme for wifi, and don’t have double NAT issue, just because you have to put the second router, in my case the extreme, in bridge mode
and it seems you connected the pr2100 by cable to the second router, and it is best on the first