@terziyski A reset to factory defaults did help. Finally. Problem solved. Thanks for the assistance. I guess it was some random issue, not a known problem with a known solution. For completeness: I...

@terziyski Thank you for your help. The contents of the label: Model: TD-W9960(EU) Ver_ 1.20 S/N: 21...... MAC: 74-....... PIN: ..... SSID: TP-Link..... I'm downloading from EU sites, firmware for...

@Sunshine The firmware fle I have is TD-W9960V1.20_1.5.0_0.8.0_up_boot(230705)_2023-07-07_17.46.00.bin size 7,800,464 bytes. I think it is the correct one.

I'm unable to upgrade the firmware. I tired the most current version and the previous version as well. Each attempt ends with "Error code: 71211". I'm sure I'm uploading a correct .bin file. What...