Hello,
I am are running the MS Online Office Server on a test system for productive use. It works fine but now I get a message that I have no license to use Excel Online?
How does the Online Office Server licensing work for using NX with Online Office Servers?
Thank you!
Nice. 
MS Online Office Server has nothing to do with Collabora Online or OnlyOffice.
I think the app Office Online integration (do you use the app?) is only a connector and you must solve your license problem with Microsoft in the Microsoft cloud where your office is running. Read also this blog entry.