BuddyPress.org

Are you running bbPress? I had the same issue, and narrowed it down to bbPress. I’ve filed a bug report here: https://bbpress.trac.wordpress.org/ticket/2161

Here’s a temporary solution that worked for me:
`function bp_fix_blog_role($blog_id, $user_id) {
add_user_to_blog($blog_id, $user_id, ‘administrator’ );
}
add_action( ‘wpmu_new_blog’, ‘bp_fix_blog_role’, 10, 2 );`

Just drop this in `mu-plugins` if you want. You can change “administrator” to whatever role you prefer. This function runs immediately after the blog is created, so it will probably solve your problem.

Code source: https://wordpress.org/support/topic/how-do-i-change-the-default-administrator-role-to-author-for-new-users