Why can't I play my old games?

I usually reload my last saves and missions while I'm trying to get all the Hard achievements in my SC2 campaign. I just updated to the latest patch today but when I tried to load my game, it said that I will have to disconnect from Battle.net and restart with the old SC2 installed.

It was totally weird, so I just shrugged and clicked yes. It then quit, then reloaded again but this time, there was no login and it auto loaded the save file. It loaded correctly, but I was not connected to Battle.net anymore and I can't open my achievements tab.

Does this mean I have to start the campaign all over again?

Solution 1:

So the way Starcraft 2 handles saves (and replays) is it keeps old copies of previous versions to run them.

BattleNet is always configured to communicate with the latest version, so if you load a previous version its not guaranteed that you'll be able to communicate, thus Blizzard doesn't provide that functionality (currently, this may change).

So do you have to start over? That save, yes. The saves you have constitute an earlier version. Now there was some discussion of playing maps/watching replays while still connected to battlenet here (its under how to run). So it may be possible to retain functionality like chat.

Your progress in the campaign doesn't need to be restarted, as campaign progress is tracked in the cloud. You can pick up your campaign where you left off.