Hi @AJW
Have you just started Boost within the last 4 hours ?
If so have a read of the last but one FAQ on this link help article below.
https://help.nowtv.com/article/what-is-now-boost
Should the Boost have been purchased more than 4 hours ago, then double check the login details on your playback devices are the same you used to purchase Boost on your account.