eNaTIS Online Booking System disfunctional

Booking slots are quite scarce which results in travelling to a DLTC which is substantial distance away. I made a learners license booking online to go to a DLTC and be told that I cannot finalize my booking as my current learners license is still valid (expires in 4 days). Why allow a booking to be made if it cannot be completed, further to this, why do I have to travel to a DLTC and wait in queues just to be told that the booking cannot be finalized.