I have checked your site and the tabs are working fine on your site on mobile devices. Check back your site after completely clearing the browser cache and check the issue.
See screenshot for clarification: https://ibb.co/jTGqT6L
Please deactivate all the 3rd party plugins and activate only theme-required plugins on the site and then check the issue. I am sure your issue will be solved. Then Activate the 3rd party plugins one by one and check which plugin is creating the issue for you.
Otherwise, if the issue still exists then keep the 3rd party plugins deactivated and share the wp logins details so i will check and give you a possible solution.
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