Thats for the simple reason that aggregates like sum, max, min are not allowed in filters.
Create the max date object in universe and use it in the report filter.
Thanks … realise this can be achieved in the universe though didn’t want to add a new object just for one report … therefore hoping for a workaround at the report level
Instead of using Y and N, have you considered using 1 and 0 and applying a ranking to it (apologies if that’s what was suggested in the link Anita posted, but equally it will save others multi-clicking through many threads. ). Rank on the top 1 and you will just have your max dates.