I would recommend checking the suggestions from this post. We often see this error when somebody has content tree-based routing enabled, and they try to visit a page for a page type which either
Does not have a view in the MVC project
Has a view with a misspelling or improper name that somehow violates the convention that the system uses to automatically find it
When the content tree based router does not find a view for the page type, according to the convention described in step 1 from this documentation it tries to load a page template. Then, if no template has been implemented yet, it throws this error.
Could this be the case for you? Do you have a view at ~/Views/Shared/PageTypes/< your page type namespace >_< your pagetype codename >.cshtml for the page type which is throwing this error?