Then try the method from the link I gave. When u use offline method you 'force' LG mobile support tool to flash kdz file of your choice - it is enough that LG MST sees any phone it can flash - it cannot check online (through IMEI I suppose) phone details.
So first download the stock .kdz of your choice,
In case of program I used and linked, you
- change two files in LG MST on your computer,
- open R&D Test tool
- select kdz file you downloaded
- press 'normal web upgrade test' button, leaving the rest as default
- wait for LG MST which opens and starts the flashing with kdz file you choosed before
Thus it is no point to let LG MST to check your phone in that method.
Before I tried it, the phone, with 'security error' message was not recognized by the PC or LG MST, even in s/w mode.