Team,
I'm unable to upgrade the firmware to recent patches Archer C20(EU)_V5_200915. Getting Error code: 4503 The uploaded file was not accepted. The reason to upgrade to this is i'm getting "This Wi-Fi network uses an older security standard that's being phased out. We recommend connecting to a different network" unable to connect to wifi automatically. Please find the reference_screenshots.zip Can you please help on this?
Probably you are trying to upgrade with a FW that is not for your region. On the bottom of teh device there should be a sticker where it is written what type of FW you have.
Follow this link to choose your location and select the right FW for your device. Then upgrade to the latest FW.
Apart from that you can try these wireless settings to see if that will suppress the message you've received appearing again:
Configure the same for 5Ghz band as well and test.