If you are getting the Incompatible version error when trying to join your server after adding Valheim Plus, please insure that you have first installed Valheim+ client side, if you haven't the guide can be found here -> https://survivalservers.com/wiki/index.php?title=How_to_Install_Valheim_Plus.
If you have already installed Valheim+ client side and are still having issues, please attempt the below fixes in order:
Fix 1:
On your control panel click on the "Modify Valheim+ Config" tool
Ensure that under the "General Server" section the following settings are check marked
Enable Settings in this Section
Enforce Mod Version Check
Scroll to the bottom and click on "Save Configuration"
Attempt to reconnect to your server, if you still get the Incompatible Version Error go to Fix #2
Fix 2:
Close down your Valheim Game
Navigate to your Valheim install location on your computer
This can be done by right clicking on Valheim in steam and selecting "manage" and "browse local files"
Go into the following folder location "BepInEx\config"
Open then valheim_plus.cfg file (Ex: notepad)
Search (Ctrl+F) for [server]
Ensure the following settings are set under the [server] heading
enabled=true
enforceMod=true
Attempt to reconnect to your server, if you still get the Incompatible Version Error go to Fix #3
Fix 3:
Close down your Valheim Game
Navigate to your Valheim install location on your computer
This can be done by right clicking on Valheim in steam and selecting "manage" and "browse local files"
Delete all of the Valheim Plus Files from this directory
BepInEx
doorstop_libs
unstripped_corlib
winhttp.dll
changelog.txt
doorstop_config.ini
In steam right click on Valheim and select "Properties"
In this menu select "Local Files"
Then select "Verify integrity of game files..."
Once Steam redownloads all game files, reinstall the latest Valheim Plus client files