the things that I add to MCreator don't appear in the game.

I imported my mod into mkreator when I added very few things there.When I tried to import the mod the second time (at the time of the second time, I added a lot of things to my mod), I made a new world and decided to check the mod. after that, I saw that I did not add new things, although they are in the creator. I think I'm importing the first version of the mod without updates. who can tell me how to fix it?