I had the same issue.
If you want to dig the treble func, please go there : FP3 custom rom development based on released source code
This will bring back your phone :
Do one slot by one:
fastboot --set-active=a
fastboot flash product product.img -S 522239K || exit 1
fastboot flash keymaster keymaster.img -S 522239K || exit 1
fastboot flash cmnlib64 cmnlib64.img -S 522239K || exit 1
fastboot flash cmnlib cmnlib.img -S 522239K || exit 1
fastboot flash lksecapp lksecapp.img -S 522239K || exit 1
fastboot flash mdtp mdtp.img -S 522239K || exit 1
fastboot flash vendor vendor.img -S 522239K || exit 1
fastboot flash system system.img -S 522239K || exit 1
fastboot flash boot boot.img -S 522239K || exit 1
fastboot flash vbmeta vbmeta.img -S 522239K || exit 1
fastboot flash dtbo dtbo.img -S 522239K || exit 1
fastboot flash dsp dsp.img -S 522239K || exit 1
fastboot flash devcfg devcfg.img -S 522239K || exit 1
fastboot flash tz tz.img -S 522239K || exit 1
fastboot flash rpm rpm.img -S 522239K || exit 1
fastboot flash sbl1 sbl1.img -S 522239K || exit 1
fastboot flash modem modem.img -S 522239K || exit 1
fastboot flash aboot aboot.img -S 522239K || exit 1
fastboot reboot bootloader
Check If youβre still in slot a! fastboot getvar current-slot
, else, try to boot on slot a.
Then slot b :
fastboot --set-active=b
fastboot flash product product.img -S 522239K || exit 1
fastboot flash keymaster keymaster.img -S 522239K || exit 1
fastboot flash cmnlib64 cmnlib64.img -S 522239K || exit 1
fastboot flash cmnlib cmnlib.img -S 522239K || exit 1
fastboot flash lksecapp lksecapp.img -S 522239K || exit 1
fastboot flash mdtp mdtp.img -S 522239K || exit 1
fastboot flash vendor vendor.img -S 522239K || exit 1
fastboot flash system system.img -S 522239K || exit 1
fastboot flash boot boot.img -S 522239K || exit 1
fastboot flash vbmeta vbmeta.img -S 522239K || exit 1
fastboot flash dtbo dtbo.img -S 522239K || exit 1
fastboot flash dsp dsp.img -S 522239K || exit 1
fastboot flash devcfg devcfg.img -S 522239K || exit 1
fastboot flash tz tz.img -S 522239K || exit 1
fastboot flash rpm rpm.img -S 522239K || exit 1
fastboot flash sbl1 sbl1.img -S 522239K || exit 1
fastboot flash modem modem.img -S 522239K || exit 1
fastboot flash aboot aboot.img -S 522239K || exit 1
fastboot reboot