In most cases, it is the result of insufficient connection between the cryptographic card and contacts in the reader.
1. Place the token with the black side facing you.
2. From the side of the golden contacts, open the cover.
3. Eject the card out by sliding the round slider towards the contacts.
4. Remove the cryptographic card from the reader.
5. Insert the cryptographic card back to the reader.
At this point, when you connect the token to your computer, the LED will be blue, which means that the cryptographic card is visible inside the reader.