Google Chat notifications not working on a Mac

Google Chat notifications on a Mac have to get through four layers: Chat's own settings, Chrome's permission for the site, macOS's settings for Chrome, and whether Chat is running at all. Work through them in order.

1. Is Chat actually running?

Your computer only gets Chat notifications from Chat open in Chrome: a chat.google.com tab, Chat in Gmail, or the Google Chat desktop app. If the Chrome profile for that account is closed, nothing will arrive, whatever your settings say. This is the most common cause for anyone with more than one Google account.

2. Chat's own notification setting

In Google Chat, open Settings and, under Desktop notifications, tick Allow chat notifications. In Gmail it's under Settings, See all settings, Chat and Meet, Manage chat settings.
Click Show example to test it. If a Turn on button appears instead, Chrome is blocking the site.
Check your status isn't Do not disturb, and that the conversation isn't muted.
If you have several accounts, each has its own notification settings, so check each one.

3. Chrome's permission for Google Chat

In Chrome, go to Settings, Privacy and security, Site settings, Notifications. Make sure https://chat.google.com and https://mail.google.com are under Allowed to send notifications, not blocked. Do this in each Chrome profile you use.

4. macOS's settings for Chrome

Open System Settings, Notifications, and choose Google Chrome. Turn on Allow notifications and pick Banners or Alerts.
If you've installed the Google Chat desktop app, it may appear separately in that list. Check it too.
Check a Focus mode isn't on. Focus can silence Chrome even when everything else is set up.

5. Your phone

Google notes that while the Google Chat mobile app is open, notifications go there rather than to your computer.

If the problem is a closed profile

ChatPager is a small Mac app that fixes this. You sign in to each Google account once, and it watches Google Chat for all of them from the menu bar, whether or not their Chrome profiles are open. When a message arrives it shows a Mac notification, and clicking it opens the conversation in the right Chrome profile. If a profile is already open, ChatPager stays quiet and lets Chrome alert you, so you don't get told twice.

It reads messages directly from Google on your Mac; nothing passes through us. It's US$19, once, with a 14-day free trial. Join the beta list to hear when it's ready to download.