I'm using a NowTV stick attached to a Samsung TV.
I had previously tried the trick to connect to Sky Store. This worked to solve the problem for a couple of days but failed this morning.
This morning I had to turn off the power to the stick while leaving the TV on. This seems to have done the trick this morning.
This was definitely down to the pihole for me. I disabled the entire thing for 30 seconds and my homepage has loaded for the first time in three weeks. Three weeks without service because NowTV seem to be insisting the device has to call out to something grabbing metrics / gathering data just to function at all. Denial of service or surveillance, wonderful.