I just purchased a TYT UV-390 (Non-GPS) on Amazon. It arrived, I unboxed it and charged it and turned it on and it's asking for a password. The same goes if I try and read or write to it using CPS MD-UV380 v1.07. The directions specifically say to use the 380 CPS with the 390 CPS resulting in an "Incorrect model number" error.
I've hit the Interwebs with a fury and tried suggested default passwords (00000000,77777777,99999999) and found CPS versions to remove passwords from MD-2017 and MD-380 models.