Yes, I have disabled the Style & Script, because I already use Bootstrap CSS und JS in my Theme, so that I don’t need it twice.
But it doesn’t make any difference, if I enable these.
The shortcode [btnclass] still does not generate any class…
[btnclass] replaced or not, if you select bootstrap btn from add-on and you theme has bootstrap css, then button should be visible properly, however, please give me temporary wp-admin login info in a private reply, I shall check the issue.