Does mobile option work when paying?

My parents are saying that when they try to pay from a mobile devise, it just sits there like it is thinking. Can you help or do I contact paypal? 

Mobile devices should allow for payment via PayPal.  Have them try using mobile FireFox or Chrome browser.  I tested your form on an Iphone 5s and it redirected to PayPal without issue even using the stock Safari browser.  As far as I can tell, your form should work on mobile.