TL-WA901ND has no such a function in range extender/repeater mode. WA850RE can make it.

Sas, did you check the Wi-Fi name and password on web interface of WR1043ND after upgrade? The NAS can detect Wi-Fi signal but cannot connect? Password is required? Any error message?

The speed of wired connection to WR841N is normal or not? Channel width is configured as 40MHz? What's the connection speed getting on wireless clients? To figure out if a specific router is abnormal...

TL-WR841N? To change login username and password, on its web interface, you can go to System Tools---Password. To change wireless username and password, first, go to Wireless---Wireless Settings to...

To get the maximum speed, it would be better to use C7 as an access point as it is a NAT device when it is a router. When connected with wan port, did you test the speed on clients connected to its...

Did you ever try to connect the printer to any other Wi-Fi networks? Change the SSID and password for C9 first. And try to reconnect via wireless config tool. If you get the same error, try to...