Cannot connect Apple Watch (original version) to iPhone 8+

I gave my Apple Watch (original version) to my daughter to use since we no longer own an iPhone. I followed all the steps to remove the activation code, but cannot get it to connect to hers (8+ model). We get to step 4 in this procedure Set up your Apple Watch - Apple Support and then it says a software update is available for the watch, but then says we must update the phone software first. So when I go to the phone software update page it says phone software IS up-to-date, running iOS 15.5. Note I shut both devices off, then restarted phone, then watch, before starting the above procedure. I have an Android (Galaxy S10e) phone and have found the connection process with both a Huawei watch and a Galaxy Watch 4 far easier than this - why is it so difficult with Apple? Seems there's a zillion others on this support forum with similar problems. Can anybody help? I don't need a referral to another support topic, tried them all already. Thanks!