@Christian_LE 

Hello, do you mean the local administrative password used to login the web interface?

If you are already in the web interface, please go to Advanced->System Tools->Administration to change the password, however, changing the local administrative password will need you to enter the old password first, so if you forgot the old password, I am afraid you will still need to reset the device to factory defaults.

  @Christian_LE 

Thank you very much for the reply.

The option to change the password is available when we login the web interface by using local password, and old password is also required to change the password, you are using TP-Link cloud account to login the web interface now, I think that is why the option disappears.

After the factory reset yesterday, normally you would be required to create a local password on you own when login at first time, do you mean that password only worked for one time and stopped working after rebooting? we didn't receive such feedback before, and could you please try factory reset one more time, and please note that this local password is different from password of TP-Link cloud account or wireless password, and please take some screenshots when you created the local password and also when trying to login after rebooting. If the problem still happens after rebooting, please let me know.