I opened my scene and now all my Octane Shaders are messed up and my scene won’t render.

This problem most likely happened because you opened your scene by double clicking on a .car file from Window Explorer. If you open a scene this way then the Octane plugin will not have a chance to initialize properly and you won’t be able to render the scene via the Octane Viewport. Always start Carrara first and then load your scene.