I am getting this error when trying to use PayPal Checkout

Had this issue with last form. Created a new form. Using paypal checkout and getting this error in sandbox.

I would recommend you to change the price of your test product, try setting up as "1" and see if that helps. 

This issue basically happens when there is a non-numeric character or a negative value in a product's price. 

If the problem persists after updating the price on the test product, let su know.