I'm using TWRP recovery to flash coz sideload is not working on my device.Make sure that you follow the install guide exactly - you may have to start over.
Install LineageOS on taimen | LineageOS Wiki
wiki.lineageos.org
Pay special notice to reboots. The Pixel has two slots for roms, and tends to change between them when you reboot the recovery. And if you reboot to the LineageOS rom before installing gapps, it can prevent them from working later on.
Can you please tell me how do I flash ???
I did this as follows -
1. clear cache
2. install Rom
3. install Gapps ( which is not successful )
4. reboot the system
...... and its reboots without Gapps
Should I change the slot from A to B in between ??? Kindly guide