[2020] Ore and oil problem!!

Make sure you grab the district tool and not one of the area tools.

https://steamcommunity.com/sharedfiles/filedetails/?id=2118597982

After painting the district, go to the industrial specialisations tab and pick the right one. Then click on the district you painted and it will be marked like in the screenshot here:

https://steamcommunity.com/sharedfiles/filedetails/?id=2118598010