Pretty much as above post; the Vehicle Unit (VU) cannot read data from the card or write data to the card.
The fact that the card has been recently downloaded doesn’t have any bearing on the matter, basically just coincidence.
Try carefully wiping the chip contact plates on the back of the card. If it still doesn’t work try it in slot 2 of the VU. If still no joy, try the card in a different VU, if possible…If it still doesn’t work you need to get the card replaced. Get hold of form D777B and fill it out, making sure you tick the box saying that you want a replacement card because the previous one is faulty. Send the form and the driver card to DVLA, suggest that you use Recorded Delivery or Special Delivery, so you at least know that they got the card back. Your new card will be sent to your home address. Do this within 7 days of to-day. Suggest you also keep a copy of the completed application form.
When driving digital vehicles you need to take a 24hr VU activity printout when you start your shift. Write on it your full name (doesn’t matter what order), your driving licence number OR your driver card number and sign the printout. Use the mode switch as you normally would during the day. Ignore the warning telling you you’re driving without a card - you know that. At the end of the shift do another VU 24hr activity printout and write on it the same three things you did for the first printout. Keep printouts for at least 29 days (after you made them) then hand in to Operator. Make sure you return any printouts before they are 42 days old. If you change vehicles mid-shift you will have to do this for each vehicle.
Carry lots of spare paper!!
You may want to do two of each printout, one for you to retain and hand one in to the operator at the end of each shift.
You can do this for a maximum of 15 days starting to-day.