Thanks for the info but I'm more than 4 months , if it is 28 activity for a month my activity count should be 112 instead of 84. But maybe I should just wait
It doesn't continue to increase from the day you register, you must be active on the forums. If you skip (don't login/post) a 2 week activity reset period then there is no way to get it back and I believe that's what happened to you.
activity is updated every hour but at what min on the zero like 1.00 2.00 3.00 12.00?
There is no specific time, it keep increasing each two weeks (from what I can see, Its like 6-7mn increase):
https://docs.google.com/spreadsheets/d/12saLhlUoqIdairxzuSPu6EYGrt7FN2lOstO1yDjCEbA/edit#gid=1012758442