@Aviani47 

Hi, the default login password is either admin in lower case or created on your own when you set it up at the first time. So if admin doesn't work either, please reset the extender to factory defaults by holding reset button until all LEDs turn on momentarily.

  @Ariwa 

Could you please let us know what kind of password do you mean?
1. If you mean the login password of your TP-Link device, it is recommended to try admin in lower case. However, if admin doesn't work and no other possible password, please reset your TP-Link device to default settings by pressing and holding the reset button for 10s. 

2. If you mean the Wi-Fi password of your TP-Link device:
For range extender, please use the Wi-Fi password of your main router to have a try, and it should be exactly the same as your main router.
For TP-Link router, please use the default Wi-Fi password to see if it works. The default Wi-Fi password is printed on the label of this device itself as wireless password/PIN. If the default password doesn't work, please reset your device to factory defaults and try again.