Answer
This generic error can have several underlying causes, so check these two things first: that every database object (views and packages) for every entity connected to the projection and its fragments actually deployed without errors (an upstream deployment failure on a related entity can surface here as this generic downstream error), and that any entity from a different component used in the projection has its component dependency properly declared on the projection itself. Working through deployment logs for the connected entities' components, rather than the projection alone, is usually where the real underlying error is found.