I have the issue that when Dawnguard is active in Data Files, that left and right mouse button wont work when
I draw my sword. Basically Left & Right hand under Controls.

I tried:

1. Placing left+ right hand control on keyboard, still wont work
2. I tried rebooting.
3. I tried running the game with only Dawnguard active in Data files, still doesnt work.
4. I unclick Dawnguard from data files and everything works again.

So it isnt a conflict with my "addons" data files. It isnt my mouse either since it works fine
in the game unless I try to use left or right hand controls.

Does anyone have a quick solution?

I feel like I payed 20 Euro for... nothing basically. Since the game isnt playble with no working attacks.

I kept on trying to fix it. Finally got it to work.

If you have the same problem -> restart -> disable Dawnguard -> log into game -> dismiss all followers you might have at the time ->
save -> log out -> reactivate Dawnguard -> log in and voila.