On this page; https://docs.gravityforms.com/security/#file-upload-security it says “There are certain extensions that Gravity Forms will always block to protect from attacks but it’s good practice to limit the extensions to the file extensions you expect to receive.”
Can I ask, what are those extensions? There’s a few image based extensions that we would like our customers to be able to upload, including .ai and .eps - but these appear to be blocked, are they in your blocked list?
Those extensions are being blocked by the WordPress mime type validation. There is a plugin you can use to enable additional extensions and mime types. See the following page of the documentation: https://docs.gravityforms.com/permitted-file-types-for-uploading/