unable to register key mdl

[Nikita17]

War3modeleditor does not open models and does not register model formats and the error "unable to register key "mdl" pops up, did everything as in the Internet and still does not work.

 

[Ravager16829]

War3modeleditor does not open models and does not register model formats and the error "unable to register key "mdl" pops up, did everything as in the Internet and still does not work.

The problem is pretty obvious. You are using the Magos' one, which is looking for the MPQ files on your installation folder.
If I remember correctly, you are using the version that doesn't have MPQ files (1.30/1.31 or Reforged use CASC).
If your installation version is 1.29 or below, running the Model Editor with Administrator right will solve this problem. If it's Reforged, I highly suggest ditching to Retera's one instead.