What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
I have checked your form and found that it works fine at the moment.
I could not find any upload file field in your form; however, upon reviewing the changes history of your form I can see you have removed such field.
Could be possible to add the field again to your form so we can test on it?
We'll wait for your response.
I add upload file fieldes, and error appeared again :(
I test submitted your form https://www.jotformeu.com/form/70186322066351 and even uploaded files. It was working just fine.
Please test again. Try also using a different browser perhaps the issue is on your browser only.
Let us know if issue still persist.