Some mods are working, some are not, can't figure out what the issue is

[Dominik Halić]

Hello there!

As mentioned in the title, I'm having an issue that I can't really solve on my own. Disclaimer: I am relatively new to Minecraft and VERY new to adding mods. I am, of course, using the Forge for all my mods and to launch my Minecraft. The version I'm using is 1.20.1-forge-47.1.0. The problem is that I can't really add some mods to my Minecraft, or rather, they don't function in game. The weird thing is that they function in single player. I'm actually mostly interested in backpacks. I tried Sophisticated Backpacks, Packed up backpacks as well as Traveler's Backpacks. I have added the required mods/dependencies as well. So, Sophisticated Core for the first one, supermartijn642 configlib and corelib for the second one. 

In singleplayer (I only tried it with Sophisticated Backpacks), the backpacks show up and they function as intended. In multiplayer, on my own server, I can get them in Creative, but I can't craft backpacks nor can I use them. When I place them on the floor, they disappear, I can't open them and when I have them in my inventory and I open a chest, for example, they just disappear. 

I checked "normal" things multiple times. I updated my Forge launcher. I made sure all mods are up to date. I even tried out Sophisticated Backpacks on their own so that there wouldn't be any possible conflict, but nothing worked. The weirdest thing to me is that JEI (Just Enough Items mod) and Xaeros Minimap work perfectly fine. I've had those two since the beginning and they have always worked without any issues. But I can't get the backpacks to work, I can't get Farmer's delight to work or Biomes of Plenty. 

My assumption is that it has something to do with my installation folders, or maybe the placement of my MC server's folder? That's the only thing I can think of, but if that's the case, I don't really know how to fix that issue. Additionally, I do not have any crash logs from today, I just have debug logs and latest logs. 

https://pastebin.com/Uuv0BTYv This is debug logs.

https://pastebin.com/E051nqj1 This is latest logs.

Apologies in advance if I made some sort of a noobie mistake or screwed up in a very obvious way, but again, I'm very new to all this, first time trying out mods on my own so I don't really know how to solve it. I appreciate the help