Once we have verified that the user has the correct role assigned, as a best practice check whether you have the license available. This step is not required if you are just creating the users but not assigning the license.
When we create a new account in Office 365, the account will not count against the subscription until we assign the license.
To check the available licenses, use the following PowerShell Cmdlet:
Get-MsolAccountSku
The following screenshot shows the output for the preceding command:
ActiveUnits will give you information about the available licenses.