My Audi suddenly cut out when starting and electric windows would not work. RAC attended and after a hour they had fault codes, mainly the cluster dash board faulty. After they left, about a hour later, I disconnected the battery and tried again, no good. A hour later I took the battery out my key, cleaned it. Put it back in. Then pressed the key near the ignition, I could not believe it, all started, no problems, Wow. 

If it's showing a faulty cluster then this will be refurbishment. As the connections can become loose. As well as the fact the imobiliser is inbuilt in the cluster which could also be the problem within the cluster