[doublepost=1528020397][/doublepost]Messages in iCloud needs two factor authentication—have you signed up for it with Apple?
Thanks. I was having the same issue, no iCloud option for Messages. I hope two-factor authentication has gotten more reliable. I enabled it when it first came out and it wreaked havoc with my Apple TVs accessing my apple account. So I disabled it and haven't tried since. But I'll give it another try for this.