To activate the purchaser categories which are used for products that are built for use with the self managed and ad hoc suppliers, please follow the below steps:
Click into the Admin Cogs along the top bar.
Click into Mini Markets on the left and into Manage Mini Markets.
Locate and access the mini market by clicking the Edit icon.
Stay on the Details tab and scroll down to the sub header Products and Categories, and check or uncheck the setting Show purchaser categories.
Then follow the guide on manually refreshing the categories and the purchaser categories will be available to be used in the mini market.