The dimension seems to not register on servers sometimes/entirely unless the host does /reload from the console and then restarts the server. Unknown cause. The dimension not being registered causes the portal to cease function.

I have the new Undergarden mod installed on my forge server, and I can build the portal and the items all exist on the server, however the portal does not teleport me to the Undergarden. I tried /reload and I stopped the server and turned it back on to no avail.

i can use this in single player but not my server i tried reloading it and nothing :( are you trying to fix it id like to play it with my friend and this is a really awesome mod

I also have the same problem in my multiplayer forge server. Creating the portal works fine, but trying to enter it does not do anything. The /reload and server restart method did not solve the issue unfortunately. However, the portal functions in single player. This is an amazing and beautiful mod that I would like to experience with friends :)

This could actually just be a problem with the current version of forge right now. I've heard that this happens to other dimension mods in 1.16, so I think this is out of Quek's control right now. However, I could be wrong about this.

It is easy to validate this (just confirmed by adding another mod with a dimension). Running "/forge dimensions" after first starting a server only shows the vanilla dimensions, but running it after restarting the server shows the vanilla and modded dimensions.

going to close this due to the bug not being my fault. it's a forge thing. now please stop asking me to fix it

As of Forge 1.16.4-35.0.15 I assume this is fixed.

the bad behavior with dimension mods is back, I'm on Forge 1.16.5-36.1.4. Works on single player not on server. All of the above statements about building the portal, activating the portal, etc are valid. I have not tried the /reload dimensions thing tho.
Can someone post a version of Forge that this works with for 1.16.5 on a server?

EDIT:

I just tested down to 36.0.46 and no dimension mod works for SMP. I only went that deep as most of the popular mods are compiled against that version of Forge. I'm curious if dimension mods for Fabric work on SMP.