Digi card not valid?

hi all i used my digi card today first time and it came up with an error( not valid )does any one have a phone (direct number) i can call about this went for a assessment yesterday and the trainer said he thinks i can call them about the fault and they send a new one, but cant seem to get any sense from dvla ,

0300 790 6109

Is the direct number for digi tacho section @ dvla

thanks ,rob