I don't think there needs to be. You wrote earlier that you applied for this card in October 2016, closed it in March 2017 and applied again in October 2017. So less than a year will have passed between bonus miles being credited and a new aplication being made and -- depending on your billing cycle -- possibly fewer than six months since the final statement.
It's possible that they're tightening up the rules but also possible that you were just a little too eager.
While I really doubt it's a hard and fast rule, mostly I've read that the safe way to go is to wait 6 months between Barclays apps. Of course I don't really know, because that's what I've been doing. Maybe if I'd pushed it more, I'd have gotten more cards, no way to know.