As time goes by, the overall pp required to achieve a certain rank increases. That means you need to gain pp faster than players around you are in order to climb the ranks.
On top of that, it takes time to derust after you take a break.
On top of THAT you need to get score that are better than the ones in your top scores list in order to even gain any pp. In your case that means scores in the high 300s, if you want to gain morw than like 1 or 2 pp. After a break, if its been long enough sometimes you can play a bunch of new maps that give lots of pp in order to replace some of the weaker scores in your top scores list, but you still need to be good enough to get good pp from those maps to do that.
Just keep playing and try not to worry about your rank so much.