Seems not to work or i dont know how to use it. 
No runs are getting tracked.

Hello, @MrVenitari.
It just should be enabled and it should track any myth+ runs.
Did you get any Lua errors?
Could you please check it with BugSack enabled (or any other errors tracker)?

Hello, not working for me either. BugSack is not showing me an errors.

Video: https://drive.google.com/file/d/1_MoR4iYEUfPJh4YZM3p6BGbUmaLwH-er/view?usp=sharing

Hi, @add1kted2ka0s. I see a problem, thanks for video report!
Could you please try to do next:

• Open file \World of Warcraft\_retail_\Interface\AddOns\MyDungeonsBook\UI\Main.lua
• Change line frame:EnableResize(false) to frame:EnableResize(true) (line 25 or close to it). This won't do any "bad" things. It just allow to resize MDB-frame.
• Reload UI (/reload) or restart WoW
• Try to open MDB /mdb
• Select some completed Mythic+
• Try to resize window (bottom right corner)

I believe it might be something with custom ui scale.