Hi @Paul Pukhtiy ,
What's the specific version of your Outlook desktop client(File>Office account>About Outlook), please first ensure that you have updated to the latest version of Outlook.
And how did the user response the meeting invitation?
According to my tests with a personal gmail account and Microsoft 365 account in Outlook 365 Version 2106 (Build 14131.20278), the meeting response I sent in the following two ways on Outlook can be viewed by Google Calendar normally.
1.click the "Accept" "Decline" option on top of invitation, if you work with this way in Outlook, it would send a respond message from your Outlook client and you could check the message in the Outlook Sent folder.
2.click"Yes""No"in the body of invitation
Please kindly check if your steps has any differences with mine, if you still need further assistace, please provide us with more information about your issues(such as client version, account type and other operation screenshoot[please note hide your personal information there]), so that I could perform more tests and provide you with more targeted help.
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