HiHi and thanks for your reply.
Just to make sure I got it right:
1. Did you flash the pie rom with the gapps or only the pie rom?
2. How did you flash the persist.img ? Via fastboot or twrp ? Newer version of twrp does not allow me to flash to the persist partition
thanks,
1) it was an attempt so I flashed rom pie + gapps, maybe it works even without gapps, I don't know.
2) for the flash I used twrp 3.3.1-0 by selecting install from the menu, it doesn't ask me where to flash, it's just done, my persist is in zip format