Messages will not download from iCloud

1. Make sure all your devices are logged in with the same Apple ID

2. Restart the Messages App

If the problem persists, then you can try to force quit the Messages app and restart it. To do this, double-click the home button or swipe up the control center to display all the apps running in the background, including Messages, then delete them all and open the Messages app again to download messages from iCloud.

3. Plug Out of Your Devices

Charging your device while sending messages is probably the cause of the problem. Therefore, to avoid this situation, it is recommended that you unplug your iPhone and then start the process again to see if downloading messages from iCloud is still stuck on the iPhone.

4. Check Network Settings

You can speed up the process of downloading messages from iCloud by checking your internet connection or network settings. Just go to iPhone "Settings"> "General"> "Reset", and then click the "Reset Network Settings" option.

5. Check Apple System Status

Please check Apple System Status is running well, you need to visit the Apple Server page to check whether the related iCloud settings are under maintenance. If not, it is not the iCloud server down that leads to iCloud messages not downloading.

6. Restart Your iPhone

Restart iPhone and download the messages from iCloud to try again.

7. Disable/Enable Messages in iCloud

Go to Settings > [Your Name] > iCloud > Turn off Messages and turn it on again after a while.

8. Sign Out of iCloud and Sign In Again.

Go to Settings > Accounts & Passwords, scroll downn to the bottom and click on "Sign Out".

Are you connected to WiFi? Is the phone plugged into a power source (not necessarily required but it sometimes helps)? Do you have power saving enabled?

How long has it been?

Are you leaving it plugged in and connected to WiFi overnight? It can take a while. If you're going in and out of the house (or wherever the network is), it will keep getting interrupted.