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The following command is very useful for debugging the OC on Windows with developer tools: "C:\Windows\SysWOW64\F12\IEChooser.exe"
To check if you have an issue with your manifest file, please try validating it with the following tool: https://github.com/OfficeDev/office-addin-validator.
If you have issues loading the Office Connector when using localhost, please try following the documentation at: https://docs.microsoft.com/en-us/office/troubleshoot/error-messages/cannot-open-add-in-from-localhost