Hello,
I haven’t updated my Steam game for about 7 months I guess before Unity 5.3 … Now I’m using Unity 5.4 and EVERY player is losing all their game data (PlayerPrefs) … what do I do? I have doubled checked I am not using PlayerPrefs.DeleteAll() anywhere.
Kas
I believe the location for saved prefs has changed on windows. There are other posts about this.
So you would basically want to copy the data over from the old location to the new - a simple detection of any empty prefs should do this. It’s a shame there’s not more information about this as it came as a surprise even to regular/hardcore unity developers like myself.
Can’t read everything 
First I’m hearing about it. This is a pretty big breaking change. Something like this should have been spelled out in big bold red letters where everyone would have a chance to see it.