This has driven me mad as I can't see why it doesn't work!
All the advice seems to point to this formula
There is a a drop down box of choices to filter the gallery and have tried to put the filter on the gallery
So dropdown box is
Name : dropdowncase
Distinct(Table1,'EHC Hub Case Number')
Filter(Table1,'EHC Hub Case Number'= dropdowncase.Selected,'EHC Hub Case Number')
Help much appreciated