Most likely because none have been assigned to the specific user account or any to any of the groups the user account has membership to.

Login into the Administration Portal, navigate to Profiles Configuration and ensure that at least one profile is assigned to the user or group that is attempting to connect through the Desktop Client.

Access settings can be edited by editing an individual profile and selecting the Access tab, located on the far right as shown below.

Adding guest access to a profile

This profile grants access rights to users with membership of the user group 'guest'.

If the user was a guest, ensure at least one profile is assigned to the user group designated for guests. See How do I Enable Guest Access?/ for further information on assigning a specific group guest access.