It is a problem, if you have uninstalled the HOTS before and try to download it again. Basically, your files are corrupted. If you want to play the game do following:
Go to your document files -> Find Heroes of the Storm -> down should be text file: variables.txt and on bottom little cross icon. It means, that file is unreadable. Remove that file. When you open HOTS again, it downloads a working file.
And I recommend you to look all files inside documents Heroes of the Storm, cause there might be more of those corrupted files that you can see by the little cross icon. Remove all of those, and the game should work as normal.
Hope this might help some of you, who had this problem :3