You go to the directory where Forsaken RO is installed, most of the time this is: "C:/Program Files/Gravity/RO/" if I'm not mistaken.
Then you search for the "fpatch.inf" file, this file contains the patch list, if it's empty it will start all over with patching.
After that, run ForsakenRO-Patcher.exe and it should repatch the fordata.grf file, after that's done, press start and hopefully things are working.