Never heard of an ISP blocking RDP traffic.
Create a rule allowing TCP traffic on port 3389. Depending on the router you may have to create a custom service (if it's not listed in preconfigured service table). Then create a rule using this service and forward to a local (NAT) IP. You can use IPCONFIG and use that IP address on the target machine if you have a DHCP scope provided by a server or the router itself. Alternatively you can specify a static local IP so you don't have to worry about it changing.
With Verizon, nothing would surprise me much anymore.
I tried to add a rule for 192.168.1.x and couldn't, I had to specify 192.168.1.4 (my primary computer's current address). It was not preconfig, so I told it custom, clear TCP/UDP 3389.
IPconfig was unnecessary, all the computers are named, and the router showed me their names and internal addresses.
Static local IP, as in fixed 192.168.1.** numbers? I'll look into that.