I've discovered the cause of the symptom. It turns out that I have two Microsoft accounts associated with the same email, an older "personal" account and an Azure "office" account. The emails were being routed to my "office" (Azure) instance and I was trying to read them from the "personal" instance.
I made this determination by adding a hardcoded email into the sender list in the Outlook step, and the email was sent properly to the hardcoded email but not to the ones being taken programmatically from the profile or the SharePoint object. The email address that Flow pulls from the profile appears correct but the email never goes there. Neither could I find the email in any junk or spam folders.
I closed all browsers out and logged back in to email online but this time selected the "office" instance associated with that email and I was able to locate the missing emails.
So this does not appear to be a Flow issue at this point and I'm assuming the Status 200 from the Flow is a success code. This was caused by having multiple MS online instances associated with the same email address, and the Flow Outlook connector preferentially used the instance I wasn't reading email from.
