To apply a filter automatically when a form is opened, specify in the OnOpen event property setting of the form either a macro that uses the ApplyFilter action or an event procedure that uses the ApplyFilter method of the DoCmd object.
Maybe on some of the ones you have trouble with, you have Filter On set to No? Not sure what the implications of that would be. I presume code would overr-ride, provided that it's placed properly. I'd also say that Activate is too late - the report is already poplualted and formatted.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.