@Kalina_mines 

Hi, do you mean the login password on the tpMiFi App?

After factory reset, the login password will be either admin in lower case or no default password and it will ask you to create a new one at the first time login. It is not the default wireless password.

If admin doesn't work and it doesn't ask you to create one at the first time login, please reset the device again by holding reset hole for about 10s, you will see "Restoring" and then "Succeed" on the screen, which means the factory reset really works.

  @Kalina_mines 

Hi, when you use a pin to press the reset hole, did you feel it really pressed something or just an empty hole?

You could try more times to reset it, also try to login the web interface to see if it makes any difference.

How to log in the management interface of 4G LTE Mobile Wi-Fi

  @Kalina_mines 

Hi, "Pin Required" means your SIM card is locked by Pin code, it will not affect the login of the tpMiFi App or web interface.

After the successful factory reset, please connect the default TP-Link WiFi with the default wireless password(8 digits, you could find it either on the label or on the screen), then disable mobile data or VPN if there is, then try to login the device via tpMiFi App or web interface, this process doesn't require internet access but you have to use the TP-Link WiFi only, so please do make sure no mobile data enabled on the phone, this default login password is either admin in lower case or no default password and ask you to create one at the first time.

If above suggestion still doesn't work, you could also insert the SIM card into another device such as your smartphone, then unlock the SIM by entering the SIM PIN lock, then disable the PIN lock, after that, you could insert the SIM back into the M7450, normally it will be plug and play since PIN lock of the SIM has been disabled.