Text predictions unexpectedly become unavailable and are missing in Outlook options

Interesting. I did some checking and, while I can find a number of posts with the issue, I've yet to find a conclusive fix. I did find one post that offered a registry edit that might work. In this post, the person was looking for a way to turn it off organization wide and found it was controlled by this registry key:

HKCU\SOFTWARE\Microsoft\Office\16.0\Common\MailSettings

Set DWORD "InlineTextPrediction" on (1) or off (0)

I checked my installation and this DWORD is not present, so it would be a default; adding it might force Outlook to show the checkbox. I cannot verify it one way or the other and if you have any reservations about editing the registry, by all means DO NOT! In several of the other posts I found, the setting came back all by itself. The post I reference is here:

https://www.reddit.com/r/sysadmin/comments/o9pit6/disable_outlook_365_text_predictions_orgwide/