Grandstram Screen Locked
On the Grandstream range of phones, there is an option to lock the keypad so that it disables all key presses on the phone. Sometimes this can be enabled by mistake leaving the user wondering what has happened.
This is really easy to remove or apply depending on what you want to happen. On the Grandstream keypad, if you press and hold the star (*) key until the LOCK symbol shows on your screen. This will then lock the keypad.
To unlock the keypad, repeat the same process as above and once unlocked, it will ask for a password. There is no password, just hit OK and this will unlock the phone.