Yes , i used the installer to create the server , and with "at first" i mean after the server was created , and i could join it , i made the batch file so i can set the amount of ram and then you guys told me to start up the jar file so i did . And i renamed it because it was a long name , something like minecraft_forge-1.12.2-1.2.3.4.5.6.7 . I've seen a lot of people with this problem , and i think we all do something wrong , i just dont get what . I saw a post , they said copy the config , i did , still doesn't work