One of the reasons why MiCollab is not making or taking calls is the softphone option is turned off.

On the bottom right corner you will see a blue text saying softphone

Click on it and enable it. That should fix the issue regarding calls.

If the problem persists, it might be worth restarting your computer.

If all else fails, please make a note of the time of the issue and send a ticket to the IT Helpdesk.