messages not updating on Mac

Hello Cris5757,

Thank you for reaching out to Apple Support Communities, and we'll be happy to help in any way we can. We understand you're having issues with missing messages on your Mac. Try the steps here if you use Messages in iCloud to keep your messages across all of your devices: Access your messages on all your Apple devices - Apple Support

"Access your messages on all your Apple devices

When you use Messages in iCloud, all the messages you send, receive, and delete are updated on all your Apple devices automatically. Keeping your messages in iCloud also helps you save space on your Mac.

To use Messages in iCloud, you need macOS 10.13.5 or later, iOS 11.4 or later, or iPadOS 13 or later. You also need to be signed in to iMessage using the same Apple ID on every device where you want to use Messages in iCloud.

Turn on Messages in iCloud

1. On your Mac, choose Apple menu  > System Settings, then do one of the following:

• If you need to sign in to your Mac: Click Sign in with your Apple ID at the top of the sidebar, then sign in with your Apple ID. Use the same Apple ID you use to sign in to Messages.
• If you’re already signed in to your Mac: Click [your name] at the top of the sidebar, then make sure you’re signed in to iCloud with the same Apple ID you use to sign in to Messages.

1. Note: Most users only have one Apple ID. If you have more than one, go to System Settings on your Mac, and Messages Settings in Messages, and make sure you’re using the same Apple ID for both.
2. Click Password & Security on the right, then make sure that Two-Factor Authentication is on. If it’s off, see Set up your Apple ID password and security information.
3. In the Messages app  on your Mac, choose Messages > Settings, then click iMessage.
4. Click Settings, then select Enable Messages in iCloud.
5. The messages from your other devices that use the same Apple ID appear on your Mac.
6. Note: Depending on how many messages you have, it may take a while for all of them to appear. You can send and receive messages during that time.

After you turn on Messages in iCloud, your messages stay up to date automatically. If you want to make sure a new change takes effect immediately, choose Messages > Settings, click iMessage, click Settings, then click Sync Now.

Turn off Messages in iCloud

You can turn off Messages in iCloud on all your devices or on your Mac only.

1. In the Messages app  on your Mac, choose Messages > Settings, then click iMessage.
2. Click Settings, then deselect Enable Messages in iCloud.
3. Choose one of the following:

• Disable All: Turns off Messages in iCloud on all your devices. Messages are no longer stored in iCloud and are instead stored on each device.
• Disable This Device: Turns off Messages in iCloud on your Mac only. Messages on your Mac are no longer stored in iCloud; on any other device where Messages in iCloud is turned on, messages continue to be stored in iCloud.

Set up iCloud for Messages on all your devices"

We hope this helps.

Cheers!