I did a variant of the original answer which seems to work so far.
i.e.: after doing this:
* Open the Excel app> go to File > options> select trust center> select trust center settings> Click on Privacy Option> Click on privacy settings > Check all the connected experiences including "Turn On experiences that download online content" and "Turn on experiences that analyze content" *
Close and reopen Excel
which didn't work, I then unchecked:
Optional diagnostic data
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Close and reopen Excel
and help was working again!
This worked for me, but originally the *Optional diagnostic data was unchecked, so I checked it. Close and reopen excel and help was working again. Thanks!