Services were disrupted earlier this afternoon (Wednesday, November 17) following a points failure at Wivelsfield.
Southern said engineers had reported that a cable had been cut and that they had to block all train lines between Haywards Heath and Brighton from 2pm to 3pm.
This also stopped services between Haywards Heath and Lewes.
The rail company has now confirmed via its Twitter account that a new cable has been installed.
“Please allow extra time to complete your journey, as services remain subject to alteration and delay,” said a spokesperson.