I attach my setting screenshot.
1) yes it is 20/40 by default, i did not change much settings.
2) did not try manual Control Channel yet
3) Tx power adjustment by default it is Performance
4) printer connection with router seems solid, the wifi indicator on the printer is all time on and signal...
ok i will everything again now, you are correct, router fw is not the latest, i am updating it now.
one more question, before i try everything, can i use router smart mode (no separate 2.4/5G SSID) if the printer can only connect thru 2.4 but at the same time the computer could connect to 2.4 or...
guys, it does not work again ....
i had the same issue (brother wireless printer can not be seen by my computer, always offline, even the printer has connected to the 2.4G SSID as same as the computer does, same network mask 192.168.1.xx) half year ago after router AX11000 firmware updated, then...