here is a thread, but it's not too useful cuz it's old:
-- Campaign Progress Lost --
There are reasons due to which your campaign progress is lost. These reasons can be limited local storage, progress not synchronized properly with the server or playing after a long time. This progress can not be brought back but, however, can be prevented in the future.
SOLUTION :
External quote.
SET THE LOCAL STORAGE TO UNLIMITED
->Go to the Play Tab from the main site.
->(ON THE LOADER :
http://prntscr.com/bwhayf) Right click and select settings
->Select the local storage menu and put the slider to the right-most side
http://prntscr.com/bwhb8pRESET THE LOCAL STORAGE
Problems can occur with your loader's storage or reducing performance ; If the above tutorial doesn't solver your problems you should :
->Go to the same Local storage menu and put the slider to the LEFT-most side
http://prntscr.com/bwhc5u->A screen will prompt asking if you want to continue or not to delete all the stored contents ; Click Yes (Make sure your progress in synchronized before making this step)
->Now Set the Local Storage to unlimited by the first tutorial.
You should reset the local storage by time ; that will boost most of your performance in game.
this might help too
http://prntscr.com/bwhdk3this image spoilers shows to u about ur game state on settings and performance
there should be something more useful here:
There is no way to recover what you've lost but there's a way to prevent it.
Check out
part 1.If your flash player's settings don't show up the sliding bar over there. Just use
this client to play. It works better and saves differential data by time.
in shortcut, there is no way to get ur own progress on ur campaign back but u can get semi-campaign progress via copying an SWF file copy and paste it into ur game state, I remember back then it was because of resetting up the cookies on ur browser but Idk really on launchers, the PB2 game is working as SWF file, and so if u moved ur SWF file from file to another then the entire progress will go... so beware not moving up ur PB2 GAme file or else u may reset up the entire progress u have made earlier... but dunno what u gotta have to do with ur level XP, that problem is too rare..but it's fine.