Just to make it clear, this is an assumption. It’s been over a year since this hack was finished, and probably over two years since that specific fix was made. The reports we had of this issue were all because of having an older save, so I’m assuming it’s exactly the same in your case, and I can’t know if it’s something else unless you send me the save file. That said…
The problem is with the save file. The first thing you should do is download the final version of the hack, regardless. If you don’t, more things that were fixed may not have been fixed in the version you have. Your old save file can still be used with the new patch.
There are two things you can do to fix the problem, that do not require playing from chapter 8 onwards again.
1-Open your .sav file in a text/hex editor, and edit the mode number (should be 1 if on prologue, which is what you don’t want) to 2. I don’t know where the mode is saved on a save file, so you’d have to look for that yourself.
2-Open the hack in FEBuilder, then press F5 to open it with the debugger attached.
Go into the Cheat tab, I highlighted where the mode number is. It should be 1, you want to change it to 2 which is for No-No mode (if you want Regi mode change it to 3). Make sure to use the same chapter number and map nodes of the chapter you’re currently at. To make sure of what those are, check the Etc. tab (top right in the image). Then save the game, and you will correctly stay in No-No mode.