Hi @EggenAnders-82
Did you mean if you create a new excel workbook in Channel>Files, it would open in browser instead of in desktop app?
I tested in my lab and it was the same behavior.
To my knowledge currently there are some issues with Excel Api in Teams, thus this behavior is by-design.
Please kindly wait for further update on this.
Thanks for your understanding and sorry for the inconvenience caused.
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