I seem to recall reading that post 2007, if the field being sorted on was not updatable, the form became not updatable when sorted on that field. IIRC, a row source using Group By or Union (can't recall about DISTINCT, DISTINCT ROW or value lists) would cause the behaviour if the form was a data sheet. Not always when something like this changes is it a bug. Sometimes it's a fix. For this one, I don't profess to know which it is, but would have to figure it has something to do with the possibility that the fixed list can't be synced with the results in some cases.
Edit: we all seem to be assuming there are no Trusted Location issues - i.e. the only thing changed was the Access version and not the pc or it's file system or the location of the db. A non trusted location will also prevent the sort.
Last edited by Micron; 05-30-2017 at 01:58 PM.
Reason: clarification
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.