ive had the same issue. I did fix it through making a new admin but also try this. I was able to get all old banks back as well.
- Open finder, use go to folder option in menu (or Shift+command+G)
2) Type:
~/Library/Application Support/Blizzard/
It will open folder contents
3) Look for “StarCraft II” folder
4) Change that folder permissions to Read and Write
* right click, GetInfo, Sharing and Permissions, unlock changes, change to RW and use small circle with dots to apply that permissions to all enclosed items.