Microsoft Outlook not previewing or showing the body of the message
It appears that a recent May 11, 2021 Microsoft Office update is impacting the previewing of messages in Outlook. It did not matter what I tried. Disabling plugins, hardware acceleration etc.
The solution is to revert Microsoft Office back to the late April 2021 and you can do this by opening command prompt as an admin equivalent in the system.
Start > Search > Command Prompt
Type: %programfiles%\Common Files\Microsoft Shared\ClickToRun
Then run: officec2rclient.exe /update user updatetoversion=16.0.11629.20246
Let the update complete. Open Outlook and it should work.
Credit: Spiceworks article.