Try using the terminal or ssh and enter the sudo raspi-config command.? Then:
1. Go to Boot Options, and change to Boot to console.?
2. Go to Interfacing Options, enable VNC.
Back out to where you can highlight finish and select it.
At the command prompt, type sudo reboot.? From now on, you can boot to the console by plugging the monitor in, or to headless by unplugging the monitor and rebooting.? I do this on my pi zero w and 3B+.
Mark,?
KE6BB?