@jmvp I installed the new version, so far so good 

  @HelpFixDecoApp Thank you. I did not know they had a pre-published feature map!

  @David-TP 

Description: After updating to firmware 1.3.1 then to 1.4.999 Build 20260319 and performing a factory reset, the router's web admin interface is inaccessible. While I can login, the web interface will not fully load.

I pulled a HAR file during the initial connection attempt, based on this:

The web interface attempts an XHR POST request to /admin/device?form=mode right after the JavaScript and CSS assets load. It immediately gets slapped with a 500 Internal Server Error. That encrypted text block in the response (zH9tcs...) states 'lan mac is nil!'

This came to light as I was developing an MCP Server for control of the Deco Platform (based on Python Library: TPLinkRouterc6u ), leveraging the local Web API.  The same lan mac is nil! is on every post-auth call, even with a fresh reboot.

I am currently in Access Point Mode.  I expected that this probably had something to do with it. Perhaps the upgrade from 1.2x to 1.3.1 may have corrupted the configuration, so I preformed the following: 

1. Enabled / Disabled DHCP - Trying to get the config file to repopulate the lan mac in the config - No Difference.
2. Enabled / Disabled Guest Wifi - Trying to get the config file to repopulate the lan mac in the config - No Difference.
3. Changed from AP mode to Router Mode, Rebooted, Changed Back, Rebooted - No Difference.  

After these tests were completed without success,  I then did a firmware update to the version 1.4.999 Build 20260319.  Hoping that the latest version of code would resolve this.  I completed the tests above again, without any success,  the web interface still does not fully load.

After doing all of this, I pulled another HAR file and ran it through AI to validate what is going on: 

(Gemini 3.1 Pro) --- Start AI Analysis ---

HAR File Analysis

• Static Assets Loaded Successfully: The browser successfully loaded the initial HTML, CSS, and JavaScript files (many served directly from the browser's memory cache).

   

• Session Timeout Detected: There is a POST request made to [http://192.168.70.185/cgi-bin/luci/;stok=/admin/system?form=envar](http://192.168.70.185/cgi-bin/luci/;stok=/admin/system?form=envar). While the server returned an HTTP 200 status, the actual JSON response body was { "success":false, "errorcode":"timeout" }. Notice that the session token (stok=) in the URL is blank.

   

• The Critical Failure (HTTP 500): The primary blocking issue is a subsequent POST request to [http://192.168.70.185/cgi-bin/luci/;stok=f<redacted>2/admin/device?form=mode](http://192.168.70.185/cgi-bin/luci/;stok=f<redacted>2/admin/device?form=mode). This request failed with a hard HTTP 500 Internal Server Error. The response body contains what appears to be an encrypted, base64-encoded string (starting with 25IGa59GHhuMC...)

--- End AI Analysis ---

Based on this, it leads me to believe either I have an edge case related to upgrade while in access point mode, or there is a bug with the web interface introduced around 1.3.1

I have several HAR files of this behavior that I can share within DM, if needed, but the core problem is still the same: lan mac is nil! fires in the LuCI dispatch function before any endpoint handler is reached, meaning it affects every single authenticated call regardless of format, protocol, or path.

  @HelpFixDecoApp : 

Thank you for your comments.  I've tried Edge, Edge In-Private, Firefox, Firefox Private Browsing to eliminate possible browser, cookie or caching issues. 

 

  @David-TP Thank you. It looks as if it is one more notch up on the firmware versions! So, maybe next release/update!  At least we are moving in the right direciton. Thank you.