Please make sure that your Key is for EyeTV 3 , not eyeTV 2 or Lite.
Ways to recover your key:
If you are old customers from Elgato, please use the following link to find the key:
https://my.eyetv.com/lost_keys?locale=en
If you are customer from us, please click the following link to find your key:
https://services.geniatech.eu/lost_keys?locale=en
More information to get your key back:
https://www.geniatech.eu/eyetv/faq/how-do-i-recover-my-lost-eyetv-activation-key/
Please show us your original purchase receipt, with it we can send you a new Key.