This issue is generally caused by a browser extension or browser setting disabling the button. Possible solutions to the issue are outlined below

Adblocker Extensions

This problem is generally caused by an adblocker being used on the computer submitting the request. Check your extensions for common Adblockers such as Ublock Origin or Adblock Plus, or common tracking protection extensions such as Privacy Badger, or Ghostry. Anti-Virus software extensions can also cause issues, such as those included with Norton or McAfee.

For more information on disabling Adblockers and other extensions please refer to the article HERE

Once the Adblocker has been disabled, please refresh the page and try uploading the document again.

Tracking Protection

In browsers such as Mozilla Firefox and Microsoft Edge, Check to see that Tracking protection is set to standard. as Strict Tracking protection will cause this problem to occur. (Note: this option is not present in Google Chrome)

To check this setting in Firefox, Navigate to the Three bars in the top left corner, and select settings

Next navigate to Privacy & Security on the left side of the screen, then ensure that Standard Tracking protection is set

After changing the setting, reload the page and check to see if the submit button is working.

Network Configuration

If the above steps fail it could be possible your network firewall is blocking the necessary flag for the page to load correctly. Try to Whitelist DAT website traffic in your network firewall, or reach out to your IT Team for assistance with this problem. For a temporary solution, try to connect to a different Wi-Fi or network connection