'Mainfest passes VisualStudio, But is invalid in Outlook

I am right now trying to create a new web add-in for Outlook.

I followed this description: https://docs.microsoft.com/en-us/office/dev/add-ins/quickstarts/outlook-quickstart?tabs=yeomangenerator

Unluckily my manifest is invalid.(outlook is telling me this after running "npm start" in VS Code) But when i try to check if it is valid in VSCode than it is saying everytime it is valid. (npm run validate)

This is the error message in Outlook: "The Outlook Developer Add-in manifest schema is invalid. Please ensure your manifest is valid and try again."

Do you have any idea how to fix this issue? Thanks.



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