Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
I don't mean to contradict Dave but 26.6.2 is not the present release of Tahoe. It's at 26.7.2 as of Oct. 26. That may not make a difference but regardless the OS should be kept current.
If you continue to have a problem be sure to provide descriptive details, includint exactly what you're attempting to install & the content of any error messages or notifications.
Note that nobody here has any access to cases opened with Microsoft or any other provider.