Not being able to pair Apple Watch with iPhone

I have recently got my Series 3 Apple Watch back out of the box after some years, (bought when first released circa 2017). the watch has been fully reset to Pair mode, when i scan it in pair mode with my phone it activates and a screen saying 'software update required before continuing' appears, i then press update now and it starts to activate then after a few seconds it comes up saying Pairing Failed and to start again, i am in a forever loop. is it still possible to update your watch even to watch OS8 even though series 3 does not support OS9???