Sign in to both devices with the same Apple ID
On iPhone, go to Settings
Tap your name
Tap iCloud
Turn on Messages
On iPad, go to Settings
Tap your name
Tap iCloud
Turn on Messages
On iPhone, go to Settings
Tap Messages
Tap Send & Receive
Make sure the same Apple ID is selected
Make sure your phone number and email address are checked
On iPad, go to Settings
Tap Messages
Tap Send & Receive
Make sure the same Apple ID is selected
Make sure your email address is checked
Keep both devices connected to Wi-Fi
Keep both devices charged
Open the Messages app on both devices
Wait for messages to sync
Restart both devices if messages do not appear
Update both devices to the latest iOS or iPadOS version