Are you able to do below from Tgx's op with the new BGN 3.5.1, I think the important step is to remove any existing versions of BGN, when doing step 4 I found more than one copy of BGN on my laptop
What version of Kodi are you using, on what platform/OS?
Install from GitHub
If you can't wait for the official skin update in Kodi add-on repository, you can manually install the latest skin revision from GitHub. Here is how:
1. Switch to the "Confluence" skin in Settings.
2. Uninstall "Black Glass Nova" from installed Addons
3. Close Kodi
4. Go into your "packages" folder:•Android -> Android/data/org.xbmc.kodi/files/.kodi/addons/packages/
•iOS -> /private/var/mobile/Library/Preferences/kodi/addons/packages/
•Linux -> ~/.kodi/addons/packages/
•Mac OS X -> /Users/<your_user_name>/Library/Application Support/kodi/addons/packages/
•OpenELEC -> /storage/.kodi/addons/packages/
•Windows XP, 7, 8 -> %appdata%\kodi\addons\packages\
and delete every file starting with "skin.blackglassnova"
5. Download the zipped skin from
https://github.com/Tgxcorporation/skin.b...helix.zip
6. Start Kodi and go to Settings -> Add-ons and select "Install from zipped file". Browse for the file downloaded in point n. 5 and press "ok". The updated skin should install.