tConvert method
If the build in method doesn’t work, you can use any XNA based converter to create the .xnb files required for the game and we’re going to tackle tConvert from Terraria to do it. First of all you can read on how to install it and use it here on the wiki, forum page or github
If you just want the software, use this link
While tConvert can do a lot of things, you’ll only need the Convert tab. Use it to convert any folder that need it and ensure that that .xnb files are in the right folders.