Why won't my previously paired iphone 6plus, IOS 12.4.4, pair with Apple watch 2?

When attempting to pair Apple watch 2 with iPhone 6plus, IOS 12.4.4, it states the phone needs to update its software. However the phone states it is up to date. Cant seem to figure out what to do next. I've reset the watch to factory settings... however that seems to have no effect.