Form Unable to use CJ Filters

Sometimes, you might find a form that, no matter what you do, simply will not allow the use of Configurable Joins in conditional logic or prompt logic. If you query the [form] table, you'll probably find that the form is very old. Further, you may notice that [form].[xml] is not null. That column has been deprecated for years.

To the best of our knowledge, any forms with [xml] data populated cannot be enabled for CJ's. Your only course of action is to copy the form and migrate to the copy.