I played SC2 human campaign just last week. I started it tonight and my only option is to start a new campaign. I tried to reload my own save file but no save files is available.
Achievements are still there. No I never switch region, only have one Bnet account.
Update:
I figured it out. Googled the problem and someone mentioned progress and saves are on local PC. My PC happened to be backing up files at the time. The progress and saves files must have been locked so SC2 couldn’t access them and think there is none.