I would suggest going to http://tyt888.com
and downloading the latest firmware for the MD390, it comes in a fairly large zip or rar file and contains a directory for each variation of MD3x0, with an without GPS where relevant and with old vocoder and new vocoder.
Direct link to the file is http://www.tyt888.com/uploadfile/upfile ... 112120.zip
The MD390 you have is a GPS version (fw says S13.009 rather than D13.009) and thus will have new vocoder so you need the S13.xxx.bin file to flash new firmware.
The CPS software for this radio is now at version 1.36 which will also be in the file you need, you'll find it in the directory for your radio which is the MD390G with GPS and new vocoder.