Mobile Install (MI) licenses are different than SI licenses. Each MI user, known as a "Mobile Installer" in SI, requires an MI license.
You automatically have an MI license for every SI license that you have.
Check Mobile Install Licences
To see how many MI licenses you have, log in to SI, click the button with your username in the upper right corner of the interface, and click My Account Information.
This will open the My Account Information form. Click the Registration tab.
You can see the number of MI licenses in the Mobile Install Seats area.
Buy Additional Licenses
If you need additional MI licenses, you can open the Mobile Installers setting in the Control Panel.
Click the Buy button on the ribbon of the Manage Mobile Installers form.