You are trying to connect a mobile device to the UMS as described under Connecting Mobile Devices to the UMS.
You can download the profile for MDM, but its installation fails.
This issue occurs because you already installed a profile in the past.
When you try to install a new profile, the old one is not automatically overwritten.
You have to manually delete the old profile.
To do this, on your mobile device, go to Settings > General > Device Management and delete the old profile.