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The OC might have some issues on Mac. Specifically, this relates to being able to open existing documents from Digizuite™ Media Manager 5 or the OC. The issues are caused by some issues with Microsoft's Office URI Scheme on Mac, which will hopefully be fixed in the future. Until then, full functionality of the OC on Mac cannot be guaranteed.
Debugging
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
If you have updated the OC and you are encountering an infinite loading spinner or the styling has become weird, please attach a debugger by following the documentation at: https://docs.microsoft.com/en-us/office/dev/add-ins/testing/debug-add-ins-using-f12-developer-tools-on-windows-10. When the debugger has been attached to the OC sideloaded in an Office application, run the command "location.reload(true)" from the console. Alternatively, you might be able to reach the debugger (and thus avoid downloading the developer tools) by opening Edge and navigating to the OC site.