We have received a couple of similar reports, which all have been resolved after the recent updates for Windows 10.
Regarding the reported issue, it seems that Windows Update is updating the audio drivers for some users. After the update process of the audio driver is finished, users report that the issue is resolved.
If you wish, you can try to manually uninstall the current audio driver and let MS Windows to automatically download and install the new audio driver.
You can do that by opening Windows Device manager and manually try to uninstall the audio driver. After the audio driver uninstall procedure is finished, you need to click on the 'Action' button -> Scan for hardware changes and let Windows to download and install the new audio driver.
Note that we recommend to ask for help from your system administrator for this procedure.
Zoiper Team cannot be held responsible if any additional issues appear with your system.