@gavs82008 Thanks for that link. I do run Bitdefender so I got excited but...
I'm looking for the NowTV app and found it in "C:\Users\me\AppData\Roaming\NOW TV\NOW TV Player\NOW TV Player.exe". However, it only allows me to turn on the Online Threat exception, and not the Advanced Threat Defense, option.
I have have found a few other threads which look at adding folders to the exception list but it hasn't helped.
appdata\roaming\Now TV Player
Again, it has set up Online Threats but not Advanced Threat exceptions, but I'm not sure if this is signfigicant.
Thank you for your help