What security patch level do you have currently?My security patch update is not on March 1 i.e latest.does it make any sense
You should be able to use a fastboot ROM with the same or newer security patch than your current system to relock your bootloader. So for example if you have NPJ25.93-14 (Dec 2016 security patch), you can use either this fastboot ROM (NPJ25.93-14, Dec 2016) https://forum.xda-developers.com/moto-g4-plus/how-to/moto-g4-plus-xt1640-43-athene-npj25-93-t3549369 or this ROM (NPJS25.93-14.4, March 2017) https://forum.xda-developers.com/moto-g4-plus/how-to/stock-rom-npjs25-93-14-4-march-1-t3608138. Either is likely to re-lock your device (though you may have to flash the full stock ROM for the relock).