I did a quick test on this under Chrome 92.0.4515.159 on MacOS and found my notifications display a preview of the incoming message. I did find though that MacOS has settings dictating when a preview is shown, and it is dependent upon the device being unlocked. Might you have security settings in place preventing the preview? Alternatively are you aware of any domain policies that might disable previews?
Kyle Kerst
IT Coordinator
SmarterTools Inc.
www.smartertools.com