When creating or editing a promotion, attempting to select a required or rewarded product in the dropdown menus on the Manage Promotions page returns an error 500 under some circumstances.
Vibe Promo for AspDotNetStorefront versions 8.x and 9.x
This issue can occur on sites with large numbers of products assigned to a single entity or if the site contains a large number of entities. This happens when the amount of data being returned to populate the dropdown menus exceeds ASP.NET's default maximum JSON length
After making a full backup of the site and database, add the following lines to the web.config file inside of the Configuration element: