You may need to disable Model Check. Follow my advice here.
http://forum.tp-link.com/showthread.php?77915-The-firmware-won-t-update&p=150530&viewfull=1#post150530

R egion : Canada

Model : TD-8816

Hardware Version : V8

Firmware Version : 8.0.0 Build 130627 Rel. 05936

Hi,

I'm having a similar problem with my TP-8816 - I get the “Error:FAIL TO UPDATE DUE TO…The upload file was not accepted by the router.” I have tried disabling Model Check, I have tried using FireFox 45, Chroma, and IE 11. I have tried all three firmware versions available for the HW (original shipping 130627, 140311, and 160112).

There is otherwise nothing wrong with it, but it seems pretty broken to me if the firmware can't be upgraded. Please help!

Thanks.

I have a TD-W8951ND Hardware version 5.1. It came installed with Firmware version 5.0.0. Build 120807 Rel. 34393. Every time I tried to update with a newer version from tp-link website it failed with (ERROR: FAIL TO UPDATE... The uploaded file was not accepted..)

This was NOT caused by trying to update over a wireless connection. I used a wired network connection.

In the end I found a solution and I have documented the process. Fact of the matter is, the update fails with certain versions of the firmware while other versions are accepted but there does not seem to be a certain logic to this. One must find out by trial and error which versions are accepted .

So my original firmware was:
120807

The upgrade failed with (ERROR: FAIL TO UPDATE... The uploaded file was not accepted..) with these versions:
140514
141114
160113

As there were no older version on the tp-link support website I was stuck with the old firmware version, that was vulnerable to the ROM-0 exploit according to
Avast network scanner.

After some research I found some older versions on Softpedia:
http://drivers.softpedia.com/downloadTag/TD-W8951NDv5

And finally with this firware version the upgrade succeeded:
http://drivers.softpedia.com/get/Router-Switch-Access-Point/TP-Link/TP-Link-TD-W8951NDv5-Router-Firmware-131104.shtml

131104
With this firmware version update succeeded.
From there on I had to use this order of version updates:
141114
160113

The modem is now on the latest firmware version and the vulnerability is no
longer reported.

techhelp wrote

I have a TD-W8951ND Hardware version 5.1. It came installed with Firmware version 5.0.0. Build 120807 Rel. 34393. Every time I tried to update with a newer version from tp-link website it failed with (ERROR: FAIL TO UPDATE... The uploaded file was not accepted..) This was NOT caused by trying to update over a wireless connection. I used a wired network connection. In the end I found a solution and I have documented the process. Fact of the matter is, the update fails with certain versions of the firmware while other versions are accepted but there does not seem to be a certain logic to this. One must find out by trial and error which versions are accepted . So my original firmware was: 120807 The upgrade failed with (ERROR: FAIL TO UPDATE... The uploaded file was not accepted..) with these versions: 140514 141114 160113 As there were no older version on the tp-link support website I was stuck with the old firmware version, that was vulnerable to the ROM-0 exploit according to Avast network scanner. After some research I found some older versions on Softpedia: http://drivers.softpedia.com/downloadTag/TD-W8951NDv5 And finally with this firware version the upgrade succeeded: http://drivers.softpedia.com/get/Router-Switch-Access-Point/TP-Link/TP-Link-TD-W8951NDv5-Router-Firmware-131104.shtml 131104 With this firmware version update succeeded. From there on I had to use this order of version updates: 141114 160113 The modem is now on the latest firmware version and the vulnerability is no longer reported.

That's great work - unfortunately, I've tried every single firmware available for my model of modem. Short of going back to older hardware revision images (which is a pretty bad idea), I don't think this strategy is going to help me. I'm wondering whether TP-Link bothers to test their products at this point.