Loading issue with steam version

[KaiH-0]

I recently build a steamos machine, I have tried to run the normal Retroarch through steam but no luck as it never appears but if not in steamos mode it does work, so instead I downloaded the retroarch steam version then put the core where it's supposed to be and gave it a go, unfortunately it came up with failed to load content. If you can help me fix this, it would be much appreciated as everything else works except this.