When you invite someone to join you on the Alterdesk messenger, this person will normally receive an invitation by email. If the invitee did not receive this email, there are a few things you can check.
First of all, ask your contact to check whether the invite has ended up in their spam folder.
If that is not the case, you might have used the wrong email address. Try again, with the correct address.
If your contact still does not receive the invite (have them check their spam folder too), please contact our helpdesk. Make sure to provide us with the name and email address of the invitee, so that we can check if he/she can be found in our system.