I am using raspberry pi 2 with latest osmc version. Recently I tried formatting SD card and again writing image on it with OSMC installer.I successfully installed OSMC and completed setup. Then I tried streaming on YouTube but it didn’t work on both wired and wireless connection.I formatted my card and installed OSMC on it again and again for 3 times but all the time it didn’t work.Internet was working when I search on YouTube it shown me results but when I click on result it show be playback failure. Then I unpacked .IMG.gz and write image on SD card with win32 dial imager and it worked. I don’t know what was the problem. Sorry but I don’t have log file. Internet was working.
I think this may be related to the API keys.
You can check with the developer of the YouTube add-on on the Kodi forum, as they may be able to provide more help.