https://docs.ficsit.app/satisfactory-modding/latest/ManualInstallDirections.html
Although I did everything right in the docs part, the SML installation occurred, but I could not activate the mods. Is there any other place where I need to install mods?
Is there anyone who can help me with this?
Don’t do this manually! Use the Modmanager but with SML 3.0 ! If you have old mods installed then de-install all mods, change the SML to 3.0 and then install the compatible mods.
I get a plugin error when I install SML 3.0. It will no longer be installed manually.
Thanks anyway mate.
I do not even see the “Install” button anymore after the 3.1 update. I installed Experimental and went to 3.1 but still did not see it. Nothing I have tried lets me see the button so I cannot use the SMM now except to update mods. I have cleared caches and cookies and reinstalled the SMM and SML over and over and nothing. It worked until that last upgrade of the SML. 3.1 requires game version 151773 and Steam version is 151248 but in the game launch it says they are the same? Frustrating. 
As far as I know mods only work in the stable version this time.
There are instructions to deal with that error message on the discord. In short, because of the difference between EA and EXP right now, there’s different SMM versions, and auto-update is temporarily disabled. Go to the discord and follow the instructions there for whichever game branch you’re using.