Thanks for the screenshot!

Just copy this on line 191:

$shortcode_2 = do_shortcode('[nostr_zap_button npub="npub1gwa27rpgum8mr9d30msg8cv7kwj2lhav2nvmdwh3wqnsa5vnudxqlta2sz" url="' . $current_url . '"]');

i removed the [ and ] surrounding your npub. That's not needed.

I ll update the documentation and mention to remove the square brackets [ and ], when replacing npub. So it's easy for non-devs too.