Hi, I'm John! I will help you with this.
First, can you let me know if you have Focused Inbox turned on in Outlook?
If so, some of your emails may be landing in the Other tab instead of Focused. Try switching to the Other tab and see if the missing messages are there. If you find any, you can move them to your Focused inbox by selecting the message and choosing Move to > Move to Focused inbox. https://support.microsoft.com/office/focused-inbox-for-outlook-f445ad7f-02f4-4294-a82e-71d8964e3978
If you’re using Outlook on iOS, Android, or a mobile browser, you can do the same by selecting the Other tab, tapping the message, and choosing the More options icon > Move to Focused inbox.
If issue persists please let me know.
Click "Add comment" to let me know.
Regards,
John J.D.