When using per User licensing, it is mandatory to enable all users that should be licensed within CRM. It often occurs, that after installing the license via the License Manager, the below screen appears:

Figure 1: License Manager - Preview License

This is due to the fact, that the user (usually an admin), who is running the license-manager is not a licensed user at this point.

To enable this, specific users you will have to follow the below steps. 

When ordering licenses, you will be asked for the organisation unit name of your CRM system. This information is mandatory in order to create a license. Below, you can find a short description about how to get the necessary information for CRM 4.0 / CRM 2011.

Check the log textbox if the following statement is present (might be accomodated by a 401 exception).

Receiving a service unavailable response on a website usually indicates, that the application pool of the site is not running.

To solve this issue, open your InternetInformation Management and verify all required app pools are started.

This article contains a detailed guide on how to find out the version number for each mscrm-addons product in CRM 4.0.