Are you using Kaspersky antivirus?
There has been an issue with Kaspersky antivirus that blocks some applications from using your microphone.
Users installing Velox desktop app for the first time or updating to a newer version of Velox desktop app may experience their microphone no longer able to be accessed by Velox desktop app.
To resolve this, please whitelist the Velox desktop application with Kaspersky antivirus, and reboot the computer. Velox desktop app should now be able to access the microphone.