tapaty

any time i download a mod pack for the server i want to join and click play, the game pops up for a split second then just brings me back to the technic app. i have tried so many ways to fix it using commands people have said to put into the terminal and text edit but they will not work!? the only thing that kinda works is hexxit where there is the launcher but all i see is white so it does not let me go anywhere im trying to fix it so i can join a moded server can anyone help!?!

i found out the problem dont worrie now it says in the terminal Error: Unable to access jarfile /Users/tapaty_to/Desktop/[mine]/TechnicLauncher.jar

it says when i try open the terminal "To view or change access privileges, select the file in the Finder and choose File > Get Info." but i have reading a writing privileges does anyone know how to fix this?!?