You are running a loop inside the function you called, so the thread is probably blocked.
Something like this could work, but idk enough about gsc to be sure.
level thread makejumppad((490.875, -2121, 134.676), (50, 0, 430));
level thread makejumppad((-2957.64, 995.975, 994.125), (50, 0, 430));
Best case would probably be that you move your loop to another function and start a thread for the loop function from makejumppad.