Hi Mark,
The AMP compatibility is provided by the plugin itself, they are the ones that gave me the code to specifically disable the close button when their plugin is enabled and the current request is an AMP request. I think it has to do with the fact that certain javascript functions need to be removed for AMP pages. This would be something to ask the plugin developers about if curious.
Either way, the close button should display on the desktop version of the site (non AMP page) because the code they told me to add in my plugin specifically uses the amp_is_request() to disable the close button and related javascript, which means if you aren’t seeing the button on non-amp pages perhaps there is an issue with your setup.
– AJ
ps: Regarding the mobile menu seems to be working now, previously the close button wasn’t there – https://a.cl.ly/4guKobJq – that said, your mobile menu is not coded with accessibility in mind – not sure what theme you are using but you may want to reach out to them at let them know since accessibility is very important. For example you should be able to hit the esc button to close the mobile menu and when tabbing through the mobile menu the focus should remain within the mobile menu.
