LG Stylo LS770 VirginMobile can’t remove FRP.

I have read all threads about removing FRP on this model

I have a phone with pattern lock. Also lockscreen says: "Call ***phone_number*** if you find this".
Can not acces settings to enable ADB – so used DOWNLOAD mode.
Tried models H631/MS631 – incorrect model ID, LS740/LS751/LS885/LS991/LS996/ – LG_suite says OK, but still see pattern after reboot.

Checking data…OK
Platform: LG Qualcomm
Selected port: COM70
Selected model: LS996
Please, put the phone into download mode manually (Power phone OFF,
press and hold "Vol+" button and connect the cable (or P990 cable)).
Reading info…
Model ID: LGLS770
IMEI: 350305-26-000000-4 <— this imei is wrong
Android version: 5.1.1
Battery level: 100%
Mode: Emergency
Initializing flash…OK
SW version: LS770ZV7_15
LAF Version: 1.1
Product ID: CH31S**********78
IMEI: 357188-**-******-3
Target operator: SPR
Hardware: rev_10
Resetting Screen Lock…OK
Reading partition…OK
Resetting FRP Lock…OK
Resetting screen lock successfully completed!
Performed by 2.2.8 software version.
Maybe the reason is newer software zv7_15 (5.1.1)?
OR I should hard reset/flash phone before reset FRP procedure?
OR maybe root before?

P.S. I wanna help to develop new LG Suite version with LS770 support. Have LS770 VirginMobile, LS770 BoostMobile, MS631 board (should be MetroPCS), Unknown carrier LS770 board…