Messaging not syncing properly

In your iPad can you see your phone number in FaceTime ? it is iMessage ON ? that is not related with the iOS 15 this features exists for long time but in your iPhone is where you should turn it on Texts Message Forwarding then your message will be synced to your iPad and you can reply from there too, go to your iPad in iMessage settings then find send & receive you have to select your apple ID and your phone number too

hi go to your iPhone settings in messages make sure that you’d iPad it’s on if not turn it back on,, iPhone and iPad must under the same Apple ID

My iPhone 12 does not have the ‘text message forwarding’ option shown above.

if you do not have another apple devices then you won't see it. that is between iPad, iPod, Mac and iPhone

Yes, my phone number is in FaceTime in my iPad settings. IMessage is ON. ‘text message forwarding’ is now showing on my iPhone, so hopefully it will now work. Thanks.

Thanks Ozzie