I have encountered the following error, which crashes as soon as I open it. I have tried uninstalling and reinstalling, changing the installation location, and other methods, but none of them have been effective. It has been a year now. Please help me solve this problem. Below is my error code CF7CD9D6-26BC-404F-892A-AB0B5587D035
If you’re getting an error code and the game forcefully shuts down during the connection process, it might be the same issue I experienced. I contacted Blizzard multiple times about this, but they neither know how to fix it nor seem interested in finding a solution.
In the end, I couldn’t fix the issue itself, but I did find a workaround that at least lets me play the game. 
In my case, the problem started after I formatted my PC and reinstalled Windows. I suspect the error occurs because the game tries to load account data from the pre-format folder/path—even though that data has already been deleted. The reason I think this is because when I try logging in with accounts I used before formatting, I get the exact same crash error.
Solution:
Create a new Battle.net ID and log in with that new account.
Then download and install the game. After doing this, the game launched and ran normally.
Downside:
The real problem is that you have to start completely from scratch. No heroes, no skins, and your level starts at 1—so you can’t even queue for Storm League. Your best bet is to grind until you can afford one of the hero bundles which is about 100-shard.
I actually left a similar comment on someone else’s post with the same issue, and they said this workaround at least allowed them to play the game again. Of course, your situation might be different—but it’s worth a try.