PayPal Checkout: Payment validation failed error when Dropdown Quantity is enabled for a product

Greetings.

I created two forms; one for individual inscription and one for group inscription (2-6).

The form for individuals is working fine and you can complete it including the payment:
https://form.jotform.co/83443449873872

The form for group inscription can be filled without problem, but when submitting the payment it shows an error:
https://form.jotform.co/83455542582866

Please see the attached image.

Can you help me?

Thank you.

I have been checking your forms and they seem to have the same settings. 

The only different I can see is the "Enable Elektronisches Lastschriftverfahren" option where on your working for is set to default on the form with the issue is set to disabled. 

May you please change this setting on the form where the issue happens and set it to default too? 

Also, upon testing the form it seems like the payment window is opening properly, the issue is when you submit the payment on PayPal and are redirected to the thank you page, correct? 

That is correct.

Now the setting that you mention are both set to default.

Did it work after making the changes?

 After the applying the changes, it is still showing the error.

I've created a sandbox form, but I cannot seem to replicate it there. Well, it's Sandbox. We cannot test your form due to the amount. Can you add a 0.50 USD item, and enable Credit Card payment? We will try it live to see if we can replicate it to your form. 

Please use this clone form with 0.50 USD items.

https://form.jotform.co/90096574149869

I can replicate the problem now. It's when a Quantity Dropdown is present for a product. I've escalated this problem to our backend team for resolution. Once we have an update, we'll let you know here. 

In the meantime, change the dropdown to a quantity box. That worked for my test form, so I'm sure that will also work to your end. 

I am not sure, but I changed the setting you suggest in the clone test form (please see the attached image).

Please confirm.

You need to edit Quantity, and choose the Box type as shown below:

OK. Done.
Can you verify?

I checked your form — https://form.jotform.co/83455542582866 and the quantity option on the payment field is still a drop-down field.

Please make sure that the changes are saved after making the update on the Quantity option.

Done.
Can you verify now?

Yes, I can confirm on my end that the quantity option of the only product of the payment field in your form — https://form.jotform.co/83455542582866 is now a Text Box, not a drop-down.