HUD speedo has stopped working

Hello fellow Prius IV owners, I do have a Japanese import ZVW50 an Active trim (I am based in the UK). Some time ago my HUD's speedo stopped working. The HUD is showing everything correctly but speedo is showing 0 all the time. I had a problem with the head unit - there was no power going into it but it was fixed and as soon as it was fixed the speedo stopped working. A coincidence? I would be very grateful for any suggestions. Thanks!