Failed authorization procedure.The client lacks sufficient authorization

[rg305]

@rayben109

# BigBlueButton landing page.
location / {
root /var/www/bigbluebutton-default;
index index.html index.htm;
expires 1m;
}

hmm...
That seems to match your --webroot command...
Let's try placing a test file there and see if it can be reached via the Internet.
echo 'testing' >> /var/www/bigbluebutton-default/test-file
then
ls -l /var/www/bigbluebutton-default/test-file

[may need sudo]