This problem happened to an end user: They would launch their Outlook 2019 or Outlook 365 product, certain messages were not in the inbox, but would show up in a search or quick search. They could also see the messages in their office portal and on their iphone.
Resetting the view or running outlook /cleanviews did not solve the issue.
First, locate the outlook data file by opening the account properties page and data files tab. Note the location of the ost file.
Then, Close Outlook.
Using file explorer, find the .ost file in the c:\users\%user%\appdata\local\microsoft\outlook folder.
Rename the .ost file to .bak or whatever you wish.
Then simply relaunch outlook, the file will be re-created and the end user should now be able to see their missing messages.