Nginx: stat() failed (13: permission denied)

Nginx operates within the directory, so if you can’t cd to that directory from the nginx user then it will fail (as does the stat command in your log). Make sure the www-user can cd all the way to the /username/test/static. You can confirm that the stat will fail or succeed by running

sudo -u www-data stat /username/test/static

In your case probably the /username directory is the issue here. Usually www-data does not have permissions to cd to other users home directories.

The best solution in that case would be to add www-data to username group:

gpasswd -a www-data username

and make sure that username group can enter all directories along the path:

chmod g+x /username && chmod g+x /username/test && chmod g+x /username/test/static

For your changes to work, restart nginx

nginx -s reload