||Guide contains spoilers, sorta||

If you are using the "Fast Travel from Anywhere" mod, this quest can be easily glitched meaning you trigger it to begin.

The reason you have probably glitched it, is because after you encountered Whoreson Junior at his estate, you probably fast travelled out somewhere. You were meant to leave the main gate to trigger a cutscene with Redanian guards which take you to King Radovid where there is a cutscene with him on his boat. After this, you leave the boat and a messenger approaches you after you walk a bit, with a letter from Triss that begins the Now or Never quest.

The easiest fix is to simply head back to Oxenfurt and approach Whoreson Junior's estate, this will sometimes trigger the Redanian cutscene. Failing this, there is a fix using the console.

To enable to console go into
C:\Program Files (x86)\Steam\steamapps\common\The Witcher 3\bin\config\base

There is a General.ini file, copy this somewhere in case you mess up and then open the file using a file reader like Notepad++.

Simply change it so that it states the following:

[General]
ConfigVersion=2
DBGConsoleOn=true


Now open the game and press the key to open console (seems to change depending on your keyboard so try ~ @ `)

In the console enter the following on seperate lines.

• addfact(q302_completed)
  
• addfact(q302_post_mafia_completed)
  
• addfact(sq302_start)

To my knowledge this skips the King Radovid sequence but should enable it so that the messenger will approach you. Do not fast travel off King Radovid's boat as a guy gives you back your weapons and the messenger should approach you shortly after walking off the boat.