I have ZBT-WE1626 connected to another router in cable in one of the LAN ports. The other router is connected to WAN. The ZBT-WE1626 in used to provide wifi access. My problem is that I cannot set a password for the wifi. And even when I somehow manage to set the password, then after power-off and power-on, again the wifi network starts open, without password.

Here's what I do:
Network--> Wifi --> edit (my wifi network)

Interface Configuration:
General Setup:  ESSID myWifi
                           Mode: Access Point
                           Network: lan  (selected)

Wireless Security:
                              Encryption WPA-PSK/EPA2-PSK Mixed Mode
                                Key  myPassword

save&apply

Encyption changed to mixed WPA/WPA2 PSK (TKIP, CCMP)
but wireless security  is :
       Cipher auto
       Key admin

And if I do poweroff and poweron (by disconnecting and reconnecting power)
then it goes back to open network with no password.

Any idea what to do?
I couldn't find a manual for this router. I got only a quick installation guide from the chinese
seller in aliexpress.
I am not an expert, although I have some technical skills.

Thanks.