I changed the player's size and now he can't walk, I already deleted the plugin, the player re-logged 20 times

I have released a new version of the plugin which prevents scaling of players, so people won't encounter this issue in the future. As for how to mitigate this specific occurrence, you will have to figure out how to fix the player yourself.

Please see my reply in the other thread where the solution was provided.
https://umod.org/community/entity-scale-manager/54073-sooo-i-did-the-thing-that-it-says-not-to-do