I have created a tab on a Facebook page with personalized content from an external server... it looks perfectly on desktop, but on mobile the tab does not even appear and I cannot find details about this on FB developers.... how can I do it that the new tab is also seen on mobile phones... I really don't think it's a problem with the code... I use the javascript API.
You can see the application from Desktop at https://www.facebook.com/studioqatro/app/1777986842510245/ But if I try to access from a mobile, it tells me that the page cannot be displayed because the link is not available, then I consider It must be something in the Facebook settings that prevents showing that tab on mobile devices
Custom Page Tabs are only supported on Desktop Web.
At the moment there is no support for them on mobile devices. This is mentioned at https://developers.facebook.com/docs/pages/tabs :