If you want to fix Launch Error (Code 2) in Skyrim: Together (Windows 10), try this;

• Go to Skyrim folder.
• Look for “st_loader.exe“.
• Rename it as “SkyrimSELauncher.exe” and save it.
• Open Steam client.
• Go to your game library.
• Launch Skyrim: Together.

Please let me know if this works for you so i can update it.