So i have been working on an animation for a few weeks and i was going to work on it today but when i tried to open the file it told me "unexpected file format" i tried uninstalling and reinstalling and it still didn't help. i noticed that the file im trying to open is the only file affected by this. every other project im working on is opening fine. does this mean i lost that file?
you can rename the fla with a rar extension and apply winrar's repair to it. if it's able to be repaired, rename it to a fla and retry opening in flash pro.
if that rails, you can unrar it and may be able to extract some of its assets for reuse in a new fla.
and, in the future, periodically save your fla's with a version number appended so you don't go through this again.