@Hank21 Thank you for the quick reply, respect to your questions and remarks:

Topic 1) The current firware that the router has is version  1.3.0 Build 20230322 Rel.70951

This update was provided by the own OMADA server as an incremental update. I always use the inbuild update icon/button when available for each device to make the firmware updates. This time, neither that icon or the official site:  https://www.tp-link.com/en/support/download/er7206/v1/#Firmware and download the binary file ER7206v1_un_1.4.0_20231114-rel36220_up_2023-11-14_10.04.07.bin after decompressed and uploaded to the omada server, in the device property tab, Config, Manage Device, Custom Upgrade option, the error is the same.

Topic 2) Please try a different browser or use incognito mode when upgrading the firmware for ER7206.
I have used Chrome, Firefox and Microsoft Edge, also the official Android OMADA app. The other devices were updated without problem, just this router.

Topic 3) Im using the latest OMADA controller version version 5.13.22 , using LAN.

Maybe this router was hacked by an organization and blocking further upgrades?

  @Clive_A Thank you for the response,

I have Java 64-bit, and reinstalled for checking if there was any change.
Today I download and installed the latest Java 64-bit from https://www.java.com/pt-BR/download/manual.jsp and still the same error for the firmware update as depicted in the following screenshot:

C:\Users\admin>java -version
java version "1.8.0_391"
Java(TM) SE Runtime Environment (build 1.8.0_391-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.391-b13, mixed mode)

This screenshots show the java version and also the OMADA UI LOG.
I can provide (if you want ) also the “Download Device Info“ of the Router, from the router properties tab, Config, Manage Device, “Download Device Info“. as sugested by the OMADA UI: “If the device has an abnormality, you can download and send to you the device information and provide it to our R&D personnel to analyze the problem.“

Or we can make a meeting using Google Meet, or TeamViewer or other software or create a ticket for a private conversation.
Thanks in advance!!

I've been trying for 2 days now upgrading my device firmware V1 from 1.2.3 Build 20221104 Rel.415001.2.3 Build 20221104 Rel.41500 TO last version 1.4 with no success , I've tried from different computers , removing JRE and installing 64bit version, trying INcongnito , I've even tried US version and the standard internationl one from the main site with no success at all  , any other ideas ... 

  @Steefozo 

I use the Oracle JavaUninstallTool.exe and delete the java 64-bit version and proceed as said on the faq website:

https://www.tp-link.com/us/support/faq/3086/

and installed instead of Oracle Java 8 64-bit version, I installed now the OpenJDK8U-jre_x64_windows_hotspot_8u392b08.msi 

The Tp-link site says:

"Download and Install OpenJDK.  OpenJDK has stopped providing Windows installers for some versions such as Java 8 and 11.

We recommend that you can use the Adoptium version. Note to download and install 64-bit version.  1) Go to Adoptium website, select Windows, x64, JRE, Version 8 or other from the drop-down menu, and click to download the installer of the .msi version."

That worked for me, I uninstall all JRE versions using the Oracle JavaUninstallerTool and installed instead the OpenJDK as the faq website said.

  @Clive_A Thats work like magic ; I did not realize there is a 1.3 version as it is not listed on the versions list , thank you for your support ...