it's difficult to help, because some information is missing:
I encountered a similar behavior with the "Attribute Slicer" from the marketplace.
After switiching the data type to "text" the visual finished more or less instantaneously (a lot of distinct values had to be rendered), fortunately this column was not needed in any date related hierarchy.
On a seond occasion I deleted the "default" visual from the report page, saved the pbix, closed pbi desktop, opened pbi dekstop, recreated the visual - voila.
Hopefully this gives you some ideas, if not please provide more info.