Puzzle Doesn't Earn Points

I got a 50 point benchmark, but when I hit next, the 50 points disappeared.

Actually, I think it happens for the points randomly.

The only time I've noticed that in the past is when I got points for a puzzle and it was the last one of a session. Then the next session, sometimes I'll get the same puzzle first and it gives the points again but shouldn't.

wait what are puzzle points? i basically only use the web