I won but I did not gain rating

You are rated much higher.
You won 0 and he lost 1.

Its because you are rated too much higher than your opponent

Usually I win 1 and he lose 1 (I have played 4 games against A-M-M, and every one I win 1)

"every one I win 1"

• So every game you go up by 1 and he goes down by 1, making the rating difference larger until you now gain 0.

@tpr said ^

"every one I win 1"

• So every game you go up by 1 and he goes down by 1, making the rating difference larger until you now gain 0.

nope but I just played one with him.
First game: +1
2nd : 1
3rd game: 1
4th : 0?
5th: 1

Your last game with +1: 1929 - 1483 = 446
The game with +0: 1926 - 1475 = 451

Your actually rating, stored inside lichess is is a number with decimals. The display rounds it to the nearest integer. When you play someone this much lower, you gain less than 1 point... Perhaps 0.7 for example. That exact change is plied to your precise rating. Sometimes that causes the displayed, rounded, rating to tick up by one, and sometimes it does not.

You either played casual which means no-one lose or
The most logical explanation is that your opponent's rating is too low
Try playing with an opponent with your rating !
Don't be scared of losing

You are making thing so much more complicated,

The reason(s) you might not gain rating is because

1. Your rating is much higher than your opponent (e.g. if you are 1900, and opponent is 1400, you may not gain rating, at most you gain 3 or 4 if you rating derivation is very high)
2. You are playing casual rated, or
3. Your account has violated the TOS (which I hope hasn’t happened to any of you)

In this circumstance, it seems to be because of reason no.1.