Can’t sent messages from my Mac

Hey there!

I don’t have all the specific details, which may help, but did you happen to follow the article provided by Apple? And if so, can you say the results of each step?:

If you can’t send or receive messages on your Mac:

https://support.apple.com/en-us/HT210057

Otherwise, if it does happen to be just a setting, or something related to the account, and is actually working as its supposed to, I’d follow this article as well, just to be sure:

Use Messages with your Mac:

https://support.apple.com/en-us/HT202549

Hope something here helps!

Please tell us which model and year Mac, and which macOS version.

To find out, click (Apple menu) > About This Mac.