Experiencing the same issue. I have a MBP 15" 2018 (Monterey 12.0.1) and a MBP 16" 2019 (Monterey 12.1). Both running Outlook 16.56 (21121100)
The MPB with Monterey 12.1 - Outlook Search does not work, only works during reindex or rebuilds. Tried all the steps, kill profiles, rename, reindex, blah blah blah... Still not working.
The MBP with Monterey 12.0.1 - Outlook Search works 100%.
Seems very likely this is a Monterey 12.1 vs Outlook issue. Glad I kept the 15" around for a just in case situation...
Now I have an email appliance (MBP 15) I get to carry around with the fancy newish MBP 16.
Hopefully for a software fix in the not too distant future. For sure won't be updating the MBP 15 anytime soon.