I tried to setup a Demand Dial Connection between 2 Servers (2019 or below).
Both of them are behind another router in different Private Subnets (Microsoft Server again) with NAT enabled.
There's a problem with L2TP + NAT so I decided to go For PPTP Protocol and I forward the PPTP port on Both NAT Servers to the Demand Dial Servers.
The problem is only one demand Dial Connection works at same time, the other one errors.
Firewall is Turned off both on Demand and Nat Servers.
All the servers are Microsoft Servers 2019 or below.
Here are some screenshots :


here is the video of the problem too :
https://www.mediafire.com/file/yrf0hcveakh266x/Tshot.mkv/file