This error means Explain Everything is unable to connect and use those devices. It's either getting blocked from doing so by the browser or the device might not be working properly. Here's what you can do:
Allow Explain Everything access those devices
Explain Everything might be blocked from accessing your microphone or camera. Please check permissions in your browser and allow Explain Everything to access those devices. Changing permission settings works differently depending on your browser. Here are the articles explaining how to change these settings:
Check if the device is connected and working properly
In other cases please make sure your microphone and camera are properly connected to your device. If this doesn't help please try updating the drivers for those devices.