Hi,
Based on the screenshot you provided, it appears that there are no licenses available to assign. This could be due to a few reasons:
User Mailboxes: This issue can occur if the user mailboxes are created in the Exchange admin center and the users aren’t yet assigned a license.
License Assignment: Ensure that the users in question have the necessary licenses assigned to them for Microsoft Teams.
Azure AD Role: Check if you have the necessary Azure AD role. You must be a Global, License, or User admin to perform the operation.
Azure Active Directory: Go to Azure Active Directory > Licenses > All products and check if Azure AD Premium P1 is listed as an assigned license.