Messages not visible on Mac mini M1

Here are some troubleshooting steps I found:

1: Make Sure the Mac has an Internet Connection

iMessage and Messages requires an internet connection to work. It doesn’t matter if the internet connection is wi-fi, ethernet, a personal hotspot, but it must be an active and functioning internet connection.

Before anything else, make sure the Mac is connected to the internet and that the internet connection works. You can test this by making sure web browsers work to browse the web, using ping, or any other method you’d like. 

2: Reboot the Mac

Often simply restarting the Mac will resolve any issues with the Messages app and iMessage not working.

1. Pull down the  Apple menu and choose “Restart”

When the Mac has booted back up again, try opening Messages and sending again.

3: Make sure Mac has Apple ID / iCloud Enabled

iMessage requires an Apple ID, which is also the same login the Mac uses for iCloud. Therefore you’ll want to make sure the Mac has the appropriate Apple ID configured:

1. From the  Apple menu, go to “System Preferences”
2. Go to “iCloud” settings and make sure that the Mac has the proper Apple ID in use. You’ll want to use the same Apple ID on the Mac that you do on your iPhone, that way Messages will sync between both devices

4: Disable & Re-enable iMessage on Mac

Sometimes disabling and then re-enabling iMessage on the Mac can resolve connection issues specific to iMessage on the Mac, here’s how to do that:

1. Open the “Messages” app on Mac
2. Pull down the “Messages” menu and choose Preferences
3. Go to the “iMessage” tab
4. Make sure the Apple ID is set properly, then check “Enable this account” is checked

5: Sign Out & Sign In to iMessage on Mac

Signing out and signing back into iMessage on the Mac will often remedy issues with Messages not working on the Mac too, here’s how to do accomplish that:

1. Open the “Messages” app on Mac
2. Pull down the “Messages” menu and choose Preferences
3. Go to the “iMessage” tab
4. Choose the “Sign Out” button
5. Quit Messages
6. Relaunch the Messages app and return back to iMessage preferences and this time sign back into the Apple ID for iMessage

6: Make Sure Message Forwarding is Enabled on iPhone

If you use an iPhone and Mac, make sure that you have enabled SMS text message forwarding and relay for iPhone and the Mac so that the Mac can relay SMS text messages to and from the iPhone through Messages. 

If that feature is not enabled, you will not be able to send SMS text messages from the Mac, meaning you wouldn’t be able to message Android users for example. 

7: Check to Make Sure iMessage Works on iPhone / iPad

If you have an iPhone or iPad as well as the Mac, make sure that iMessage is working on that device as well. 

If the iPhone or iPad is experiencing issues or showing waiting for activation error or similar, it’s also possible there are issues with Apple iMessage servers being down.

iMessage is working, but not syncing with other devices properly

Sometimes iMessage works, but you’ll find that messages are not always syncing between the Mac and iPhone or other devices. If that’s the case, learn how to fix iMessage not syncing between Mac and iPhone properly here.

iMessage works, but seeing “Not Sent” errors

If you have iMessage working on the Mac but you are repeatedly seeing Message Not Sent errors, go here to read about resolving that issue.

I found this article from https://osxdaily.com/2020/02/04/imessage-not-working-mac-fix-troubleshooting-messages/#:~:text=Troubleshooting%20Messages%20Not%20Working%20in%20MacOS%201%20Make,In%20to%20iMessage%20on%20Mac%20More%20items...%20

I hope this helps!