I ran into a stubborn error message trying to connect to a catalog list defined on another site collection. The error was:
Some tagging field(s) “owstaxidSector,owstaxidRegion,owstaxidProductx0020Class,” in the shared catalog could not be found in search schema.
Now when I checked the catalog site search schema (can be found under Site Settings -> Search -> Schema), those columns weren’t there. So: valid error message. But why weren’t they? I had created the site columns, added them to a content type, put the content type in the catalog list and I was perfectly capably of selecting them in the catalog settings.
This is a little SharePoint gotcha: a column will only get created as managed property in search when SharePoint finds actual values for it during an indexing run. So when you create your list, create at least one item in it which has values for every single field you want to use as a managed property in search. You can delete that item afterwards if you want to, search won’t delete the managed property.