Hello Sheldon Wolfe,
First, check whether the missing messages appear in Gmail on the web under Sent Mail.
If they are there, Gmail has stored them correctly and the issue is likely Outlook’s IMAP folder mapping. In Classic Outlook, expand the Gmail account and check whether the messages appear under another folder such as [Gmail] > Sent Mail. Also right-click the Gmail account, select IMAP Folders, choose Query, and confirm that Gmail’s Sent Mail folder is subscribed.
Microsoft also recommends enabling Show in IMAP for Sent Mail under Gmail Settings > See all settings > Labels:
Fix problems connecting your Google account to the Microsoft Cloud
If Sent Mail is visible in Gmail and subscribed in Outlook but remains empty, please confirm that detail. A closely matching case indicates that Outlook’s local Gmail folder mapping or cache may then need to be reset:
Sent items in Gmail do not show in Outlook