Dropdown filter keeps changing to list in published version

Hi Jens
Enjoyed the course on Monday, and have now created a report.
I have data plotted on a map (using Lats, Longs) although there is also a site name and country in the various data fields.
I would like to be able to filter on country and/or site name, and this works OK in PowerBI desktop, but when I publish the report, the dropdown Country filter changes from a look up to a list. (The Site filter stays as a lookup OK.)
Any ideas?
Thanks,

Val.