So, My friend and I were playing Minecraft on our server. 
When we want to go to the nether, the portal teleports us to the same exact X and Z coordinates as overworld and without any portal generates.

Note:

The server is laggy at that time. it took more than one minute to teleport us to the nether.

I also attach the screenshot of my device and our server properties

*I don't know where to find the game log