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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 just checked your form and I was not able to replicate the problem. Can you confirm that the file you're trying to upload has the correct and allowed file type extension?
You may also modify your upload field's file type extension as provided on this user guide: https://www.jotform.com/help/29-How-to-Change-the-Allowed-File-Types-Extensions-in-the-Upload-Field
If the problem persists, please let us know.