There has been a few reports on this.
What playback devices are you using and are you using a VPN.
Also who is your Broadband provider.
First thing I would try is to switch the power off on the Router for around 30 minutes to acquire a new IP address, just in case NOW can't recognise your IP location.
Hello there, I’m using a fire tv stick / plusnet broadband. Turned off the router, but still getting the same message. Must be a fault with NOW if others are experiencing the same issue. They don’t even have a contract number, & they’re part of SKY! Unbelievable.
I have just noticed this red service banner on the NOW Help Centre (see screenshot below).
NOW is currently playing fine for me, but it must be affecting a lot of customers if this message is up on their website.