Installing private signed Addon using standard installation folder not working

Hi All,

i am developing an addon for private use. Unfortunately I failed to install it using the standard extension folders (…\AppData\Roaming\Mozilla\Extensions…) although i followed these instructions. (“Installation using the standard extension folders”).

Installation the Addon from file works but I want to use the “…AppData\Roaming\Mozilla\Extensions…” folder… What am I missing?

Firefox (64bit) is up to date (67.0.4) and I am running windows 10.