If you try to install add-ons in Dreamweaver for non-english locales, the extension does not load in Dreamweaver.

Reason

This issue occurs because a different language pack folder is created in user app data and the extension files are getting copied there.

For example, in Japanese Dreamweaver, the en_US folder gets created in user app data and extension files get copied into it instead of the ja_JP folder.

Because of this, you get a message that the extension is installed successfully, however the extension does not load in Dreamweaver because it is in the wrong folder.

Workaround

Manually copying the extension files to the correct language pack might in some cases, resolve this issue. 

However, if you want to remove the extension from Dreamweaver later on, you will have to manually delete the extension files.