Conflict With Ninja Forms File Upload

I recently purchased Ninja Forms File Upload and discovered that there is a conflict which prevents the file upload from working. Initially we suspected the conflict was with Elementor, but the Ninja Forms support team helped me to narrow this issue down to a conflict between Ninja Forms File Upload and the plugin Popup Maker v1.16.1.

Procedure to Reproduce the Issue
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1. Open browser and navigate to https://nextid.com/authenticity which is a simple form.
2. Add some dummy values to the fields until the only item left is ‘Upload your artwork’.
3. Click on ‘Select file’ and notice that the warning “This is a required field” appears along with an exclamation mark, even before submitting the form.
4. In the dialog that appears, you may select any file to upload. When you click ‘Open’ you would expect to see a file upload indicated by the progress bar, but none appears.
5. Click ‘Submit’ and notice that the form is NOT submitted because it is missing a required field (the file upload).
6. De-activate the Popup Maker plugin, refresh the page with the form and repeat the steps above.
7. Notice especially that there is no warning when you select the file, that after the file is selected, a progress bar is shown to indicate the file upload in progress, after a few moments the filename is shown along with a button to delete it if desired, and finally that you are able to submit the completed form.

Recording: https://www.dropbox.com/s/jusce1p8sfbdnpw/ninja_forms_file_upload_failure.mp4?dl=0

The page I need help with: [log in to see the link]