Create options missing from Material Request

Howdy! I’m in the process of customising ERPNext for myself and have hit a bit of a weird issue I cannot work out…

I can create a Material Request from a Sales Order (great) but after submitting the Material Request I get no options for creating a Purchase Order or doing anything else. Simply a blank dropdown? Likewise, when I try to create a Purchase Order from a Material Request there is nothing listed.

This topic mentioned info in products could be the cause but no explanation of exactly what info might be missing? Any help greatly appreciated!