This from italki Support::
(drop down menu next to your italki profile picture and select Support, then search for skype)
There are two types of Skype accounts:
<ul><li>Skype accounts with a username. This username is what we call a Skype ID.</li><li>Skype accounts with an email address attached to a Microsoft account. This is the account you use for Microsoft Products (Windows, Xbox etc.). This means that your account ID is your Live ID, e.g. italki_320941. </li></ul><em>We recommend that you use a Skype account with a Skype ID because an email address can be linked to multiple accounts, while Skype IDs are unique.</em>
To find your Skype ID on Windows, simply select your profile picture, and your Skype name will be displayed in your profile next to "Signed in as".
So in other words - it works fine with email ID but your email isn't unique so a search might find more than one possible account. If the person you want to talk to has a unique skype ID it might be simplest if you message/call them the first time that way they won't have any confusion about finding you