Hi @Tracy Louis-Marie
Can you tell us how did you install this trial version of Microsoft 365 Apps?
Is Office currently in the valid trial period?
Sometimes, because of the update channel of Microsoft 365 Apps, version name, or version number, etc., there will be differences in functionality.
It's recommened to go to Options > Customize Ribbon
, under "Customize the Ribbon:" on the far right, look for "Main Tabs" > "View" > "Windows", check whether there is "View Side by Side".
IF not, you can locate to "Choose commands from:", select " All Commands" and try to find "View Side by Side".
Once you find it, you can click "New Group" and add it to the new group.
IF you do not find "View Side by Side" as above steps, for better analysis, could you please take some screenshots and paste here?
I would suggest you go to Word > Account > Product Information
, check the Version Name and Version Numbet.
Thanks for your understandings.
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