ShaderFX displays various error messages at the bottom of the work area for Interactive graphs.
Note: In 3ds Max 2018.4 Update, the Stingray physically-based shader is renamed
Interactive.
Note: Unlike ShaderFX, the Interactive shader is sensitive to the order in which you connect nodes. For example, a subgraph must be complete and correct before you wire it to an input of (for example) the Standard Base node.
In the ShaderFX editor for your Interactive network, if you perform an illegal operation, such as multiplying a float2 by a float3, you obtain an error :Swatch Rendering not supported for this node at this time" when you click the Render Swatch
icon. In other words, your swatch does not compile. Choose Settings 
Show Swatch Compile Errors, then click the Render Swatch icon and inspect the errors that appear in the ShaderFX editor window.