The sudden failure of your set-up is a bit of a mystery. The basic question is whether it is a failure of your system to recognize the USB adapter, a failure of the adapter, or a problem with the microphone. Below is some information taken from our Microphone Set-Up and Troubleshooting Guide which can be read in its entirety at:
Troubleshooting a Microphone Not Working at All
This is a rare situation, but one which leads to great frustration. Keep in mind that Dragon will only use a microphone that is being recognized by the operating system. So after visually inspecting the microphone to rule out obvious mechanical issues, you should take steps to assure that the operating system is recognizing the microphone.
Here is our basic protocol:
Visually inspect the microphone and cord (and external sound device if being used) to be sure there is no evidence of damage to the wire.
Be sure your microphone doesn’t have a mute switch. If so, be sure that the muting function is not activated
If you are using a USB adapter, be sure that it doesn’t have a mute switch, and if it does, be sure the sound is not being muted.
If possible, use the microphone with another application, either on your current computer or another to assess its integrity in another environment. For instance, try your microphone with Skype or another audio application which uses a microphone.
Confirm that your operating system is sensing the microphone:
Windows 8: Go to Control Panel > Sound > Recording tab. You should see you microphone and when talking, you see green deflections in the sound magnitude scale. If you search “sound recorder” on Windows 8 it will launch a sound recorder which can be used to record a sample recording for use in assessing microphone sound quality.
Windows 7 & Vista: Go to your Control Panel > Hardware and Sound > Sound, and click on the recording tab. You should see your microphone. When talking, you should see deflections in the green sound magnitude scale.
Windows XP: Confirming a microphone is more difficult in XP than in 7. Often, the simplest method is to try a sample sound recording. This is done as follows:
Click on Start > All Programs > Accessories > Entertainment > Sound Recorder
On the sound recorder Edit menu, select Audio Properties
Under the Sound Recording section, be sure your sound device is correctly chosen (select your on-board sound card if using a microphone plugged into the mic and sound jacks; if using a USB microphone or device, select the name corresponding to the device – many USB sound adapters show up as AK5370 in windows XP)
Make a sample recording by clicking on the record button. If audio is being recorded you will see deviations in the green signal line in the center of the recording.
Hit the rewind button to bring you back to the beginning of the recording
Hit the play button and listen to the recording
If you are using a laptop and have a microphone plugged into the sound-out and microphone jacks, it should be disabling the on-board microphone, but there are many examples of this not being the case. It is possible that Dragon is taking the sound signal from the on-board microphone and not the microphone you have plugged in. In this case you should attempt manually disable the on-board microphone. This method varies from machine to machine and may not be possible. As a last resort (but nonetheless an excellent solution), get yourself an external USB sound adapter and do away with the problem. Dragon will be directed to take it sound signal from the USB device into which you microphone is plugged and the on-board microphone will no longer harass you!
If you are plugging your microphone into the sound and microphone jacks on your computer, confirm that you have these properly selected. In general the sound jack is marked in green and the microphone jack in pink or red. If you have more than one set of jacks (front and rear), try plugging the microphone into the other set. If you know your microphone is otherwise working but not with your PC, consider the route of using an external USB sound adapter.
Please let us know if this information doesn't get the problem solved or at least the culprit identified. Worse case scenario, we are happy to inspect and test your USB adapter and microphone to see which (if either) is at fault.