Hello Diena,
Thank you for the details. I checked this for you and this is resolved, please delete your cache and view your URL at http://23cdbbdca7ba48eeab622d5fda42ce2a.testing-url.ws/product/city-tours-in-europe/ and it will show the tabs normally.
This issue is that you many cache and minify plugins, you have:
Autoptimize
WordPress Minify
Fast Velocity Minify
W3 Total Cache
WP Smush
WP Super Cache
Almost all of these plugins when installed and first activated makes changes or adds specific code to your WordPress install. You can most certainly use a cache plugin, but try using only one otherwise those plugins conflict between themselves and create issues like these which is not related to the theme but caused by plugins. Also, test when you add a plugin and follow their recommendations.
I have deactivated them for you and you can activate them back one by one to check the plugin that causes this issue and edit the settings.
Thank you