@kefah Try to upgrade TL-WR940N_V2_130709 or TL-WR940N_V2_140627 first.

With random disconnection, how about status of lights on powerline adapters? Check status of local area connection. Any IP address obtained? Try to disable power saving....

Did you contact tikona to confirm network parameters such as VPI, VCI, connection type, username and password? If you have, you can login web interface of W8961 to set it up. If it is too difficult...

So you are trying to upgrade a third party firmware?

Is it possible for you to install the adapter on a different computer and test if the problem continues? If it is the same, maybe the adapter is defective...

I'm afraid not. We can only customerize extender's SSID. Its password cannot be changed and it should be the same as the main router's Wi-Fi password.