How to correctly place the skype button on the site for voice calls (some calls do not go through)?

Question

Skype

We have a page with 3 managers on it, under each link "call via Skype".
The links are implemented as follows:
<a href="skype:%skypeUsername%">Скайп</a>
The call goes only for the 1st user, whose account was opened a long time ago, through the Skype service itself (Skype: username is written in the personal information). Also the call goes through to me, the account was registered also.
2 other managers in have logins like dcf56****41cb5. The call does not go through, starts ringing and hangs up. Skype says "Subscriber dcf56****41cb5 is not responding."
Managers were sent instructions on how to set up Skype to receive calls not from the contact list ( link )
They say everything is set up. Calls to 2 problem accounts do not go through
Tried to change the link code like this:
<a href="skype:%skypeUsername%?call">Скайп</a>
Calls do not go through
Googled the problem, from where I found out that since some time people have been registering not through a Skype account, but a Microsoft account, from where logins like dcf56 **** 41cb5 appear (maybe I misunderstood something and now I'm misleading , and the problem is not the type of account). I found the official service that generates the button code (html + js). I put a test on 1 link to eliminate js conflict - it doesn't work.
Questions: how did you implement it? what could be the problem (like copy-pasting several times, there should be no typos)?

Answer 1

The code is essentially correct https://msdn.microsoft.com/library/office/dn745878
Most likely something on the side of the managers