Help; I tried to register my device and my serial number isn't working.

Don't panic, you might just need to double check the numbers and letters in the serial number that you received.  A common error is confusing a Zero for an "O," an "I" as a 1, or even a "W" as two "Vs."  Also, make sure that you have the correct app installed on your smartphone for the EyeQue Personal Vision Tracker device you are going to use.  If you use the serial number for the Personal Vision Tracker on the Insight app then it will not work; the same goes for the inverse. The VisionCheck app does not require a serial number. If you feel that, after trying the alternate letter; number or app, that the serial number is incorrect, please contact [e-mail] and the customer support team will be happy to help you further.