Do_shortcode doesn't work

Did you echo the do_shortcode()?

Yes, of course:

<?php
echo do_shortcode('[tabby title="Tab1"]');
?>
content
<?php
echo do_shortcode('[tabbyending]');
?>

Please link to a page on your site where this should appear, and indicate where on the page you expect it to appear.

E.g. at https://lab.fmk.sk/profil/jan-visnovsky
It should appear like at https://fmk.sk/profil/jan-visnovsky/

The issue appears to be that the javascript is not loading. This may be caused by another plugin or by the theme.

To troubleshoot, first deactivate all other plugins. If the javascript loads and the the tabs appear then activate the plugins one by one to identify the one causing the issue.

The theme you are using does not appear to be listed on www.ads-software.com theme directory, so I do not know whether it is coded to normal WordPress standards as it would not have been passed by the theme review team.

Troubleshooting the theme is not as easy as looking for a theme issue would normally be as you would need to emulate the code you have added to your template on the default twentyfifteen theme to check whether it works when your theme is taken out of the equation.

Thanks for hint. I don’t understand that I didn’t notice. Footer (and all scripts) is missing ?? Thanks again. I am going to fix it.

If it is a theme issue, the first thing to check would be that your footer.php (or possibly another file depending on how the theme is built) correctly includes the mandatory wp_footer() hook.

Fixed. Finally works. ??

great! Feel free to leave a review of the plugin if you are enjoying it.