Why form does not redirect to PayPal payment page?

Hello- We currently have a form that we're using where we ask how the customer would like to pay. Check or credit card. It's set up to send them to paypal if they wish to pay via credit card. It had been working really great up until this week and it's no longer redirecting them. Just wondering if there is something that we can do to get it working again. 

Thank you,

Sarah

Currently your payment field is not required and this is why your users may simply submit the form without even filling out the payment field. 

Please set the field as  required, this way when the payment field is shown it will ask to be filled and redirect to PayPal as  well.

Hope this helps.