Why my PayPal form is not working?

I have a series of forms and one's Paypal link works fine, but the other isn't.  I can't seem to locate the difference between the two.. what am I missing?

Do you get any error message when you submit your form?

I did test your form and I did not find any issue with that. I was able to submit your form successfully and I was redirected to PayPal checkout page. Please check the screenshot below:

I would suggest you to please test your form again and get back to us if you have any trouble. You may also like to share a screenshot of the problem and we will take a look. The following guide should help you how to upload image in forum post:  https://www.jotform.com/help/438-How-to-Post-Screenshots-to-Our-Support-Forum

We will wait for your response.

Weird... it just stops when I try at the final submit page; no error,
nothing happens at all - it just sits there. Also, it doesn't appear to
function on my phone either. Are the forms not mobile friendly?
...

I have tested the form from my end as my colleague did also and i could not replicate the problem you are having on your end. I would recommend you clear your browser cache and test it again.

Also on working on the phone I have tested and below are my screenshots of the form in my phone.