How come mobile users cannot access form on Facebook page?

I have added my form to my page on facebook but people that are mobile cannot access it, can you please tell me why?

Unfortunately, Facebook does not support Tabs on the mobile website.

What you can try is adding a direct form link as a Contact Us button on your Facebook page.

Alternatively, this is possible to embed the form with a 'Static HTML: iframe tabs' Tab App:

Adding a form to Facebook (Custom iFrame App)

They provide a special Tab link for mobile devices.

Then, you can also use that mobile Tab link as the Contact Us button link.

If you need any further assistance, please let us know.