Hey David. I had this problem a couple of weeks ago and posted a review on the app store. 

The team at dyson responded and got me to do a reset. Basically I unplugged my machine for a few minutes and when I plugged it back in, it ‘refreshed’ the connection and started to work. 

Hopefully this has helped. 

Emma :)

Thanks @Emma.S its fixed now. Hopefully this will work in the future as well.

David.