Use IE or FF as a browse, do not use Chrome.
If you still have access thru the page, use that, if not, try the button. Then attempt to send the file using IE or FF. If it works and processes the file, do one more factory reset when the modem comes back to ready after the FW update completes, then set up the modem.
IF this fails, you'll need to contact your regional D-Link support office and inquire as to why this version is failing to update.