Hey there,

Welcome to Kadence Support.

It looks this could come from a Customizer Setting. Can you go to your Customizer -> Header and click on the Design Tab. Then, look for the Screen size to switch to mobile header setting. Here is a clip for reference: https://share.zight.com/JruE5D47.

If this setting isn’t the cause. You should ensure that your Mobile Header is set with a Trigger in it and your Mobile Navigation is put inside of the Off Canvas Area. Here is a video for reference: https://share.zight.com/rRuDBjBb.

Additionally, this could come from Caching. I noticed your website is optimized. If the method above doesn’t work, you may have an Optimization Setting interfering with your Header. To test this, try temporarily deactivating your Cache Plugin. Then, clear all of your Caches and see if the issue continues.

If the issue goes away, you should Troubleshoot your Optimization Settings. You can do so by activating your Optimization Plugin again and disable each setting one by one. Each time you disable a setting, clear all of your Caches and check to see if the issue occurs. Once the issue occurs after disabling a specific setting, you may need to exclude one of our files from being optimized.

If you find a Setting causing this from your Optimization/Cache plugin, try excluding the following file from that form of optimization and see if the Mobile Header works for you then.
navigation.min.js

I hope this was helpful. Please let me know if this works for you.

Best regards,
Victor