Enrolling your Mac
Enrolling macOS versions older than 10.14 is not supported any more.
On recent versions of macOS two profiles are downloaded and installed (first a "CA Certificate" and then an "MDM Profile"), for each of these the user is asked several times for confirmation. The framework and the Self-Service app are then pushed from the server in the background. Due to this it might take a few minutes until the Self-Service app is installed on newer versions of macOS.
To enrol your Mac simply visit https://mdm.cern.ch/enrol. You will be asked first to download and install a "CA Certificate". When that is done go back to the browser window to download and install the "MDM Profile".
Older versions of macOS automatically opened "System Prefenrences / Profiles" when these files were downlaoded. On recent versions of macOS this is not the case any more - you now have to open "System Prefenrences / Profiles" yurself. You will be asked several times to confirm that you want to install these files. Once both files are installed you can quit your browser, the installation of the framework and the Self-Service app will happen automatically in the background. Within a few minutes the Self-Service app should appear in your Applications folder.
The Mac Self-Service only shows 'free' configs and apps on devices that just have been enrolled. It can take up to 15 minutes until licensed software packages become available.