Hi Mike,
Thanks for your reply.
There may be an issue with the hard drive if you're unable to play any recording a second time.
If resetting your V6 by the mains doesn't work then I'd recommend clearing the hard drive but this would result in your recordings being wiped.
This way you should be able to continue recording as normal but if the issue isn't resolved then we would need to arrange for a technician.
I have added a link here which will explain the different options and which steps to take regarding clearing your recordings.
Please let me know how you get on