FAQ: What are some common questions about ArcGIS Pro Licensing?
Question 1: What do I do if the Manage Licensing button is missing from ArcGIS Online (not Portal)?
Answer: The organization's administrator must contact Customer Service so that the organization’s ArcGIS Pro licenses can be provisioned to use for ArcGIS Online. Once licenses are provisioned by Customer Service, the administrator can then assign, revoke, and change ArcGIS Pro licenses within their organization using their ArcGIS Online account.
Note:
Only organization administrators can manage licenses, for others the Manage Licensing button is not visible.
tq Mr... sorry for late reply