If desktop notifications were enabled on your messages, but you aren't getting notifications, you may need to check your operating system notification settings. Here's how:
Windows 10
Click on the notifications icon at the bottom right corner of your taskbar, then click the expand button if your settings dashboard is not already expanded.
Make sure that Focus Assist is turned off. Focus Assist prevents notifications from being displayed.
Click the All settings icon in your settings dashboard. In the all settings menu, type "Notifications" in the search at the top of the page and select "Notifications & Actions settings".
In the Notifications and Actions settings screen, scroll down and find Google Chrome. Make sure that Chrome has notifications turned on.
Windows 11
In Windows 11, the steps are similar. Click the Date/Time at the bottom right corner of your taskbar, then make sure the Do not disturb is off by hovering over the Do not disturb icon. If the Do not disturb mode is on, it prevents notifications from being displayed.
Right-click the Do not disturb icon or enable Do not disturb temporarily to see the Notification settings link.
Click the link to go to Notification settings. In the Notifications and Actions settings screen, scroll down and find Google Chrome. Make sure that Chrome has notifications turned on.
Mac OSX
Click the Date/Time at the top right of the screen or swipe left with two fingers from the right edge of the trackpad to open Notification Center and make sure Do Not Disturb is turned off.
Open System Preferences and select Notifications & Focus.
Scroll down to Google Chrome. Make sure Chrome has either Banners or Alerts enabled.