Update - 23/09
A patch has now been released that should fix this issue. You may need to update your device, to do this:
Home x5Fast Forward x3Rewind x2
If you still see the issue after updating please let us know by replying here.
We're aware of some sticks showing "Sorry NOW TV is currently unavailable when trying to watch content. We're working hard to fix this issue and will update customers when we have a resolution.
Meanwhile, as a possible workaround to this problem - pressing the back (arrow) button on your NOW TV remote should dismiss the the message and allow you to continue
NOW TV Team