Hi Antoine,
Thanks for reaching out.
It has been found that the website is using a much older version Pro i.e. 2.0.4. I would suggest you update the Pro to its latest version i.e. 4.3.3 and check if that resolves that issue.
If that does not, there might be some different reasons behind your issue, I would like to suggest troubleshoot the following common issue to help us to recognize the reason.
1.Plugin Conflict
2.Theme Update related issue
3.Child Theme Related issue
4.CSS/JS Customization
5.Disabling Cache
If you discover that an issue is coming from a custom code or 3rd party plugin, kindly consult with a developer or contact the plugin author. Please note that we do not provide support for custom codes and 3rd party plugins.
If none of the above helps and you are still getting the issue, please provide login credentials for your site in a secure note to examine it further, including:
– WordPress Site URL & Login URL
– WordPress Admin username/password
To create a secure note, click the key icon underneath any of your posts.
Thanks