I’ve had my now tv black box for a few years. No problems. Worked fine last night. Turning on my tv today just doesn’t connect to it. I’ve not changed anything, I’ve tried it on another tv - doesn’t connect. I’ve tried resetting it. The white light keeps flashing. I’ve reset the internet. Have honestly no idea
Have you tried a full factory reset by pushing a pin in the reset hole on the back of the box for about 30 seconds whilst the TV and box is switched on.
Once you have factory reset the box, you will have to setup the box again from scratch.
Only factory reset the box if you have the physical NOW remote.
I would try a factory reset one more time.
If your Router is dual band, try both the 2.4ghz and 5ghz wifi frequencies.
Also if you can getaway with an Ethernet cable, try an Ethernet cable between the Router and box.
When you say the box doesn't connect, i am assuming it's regarding the wifi connection and you don't mean the TV screen is blank which would point more towards a possible HDMI issue or another problem with the NOW box.
Usually a flashing white light on the box could be a couple of things, such has no internet connection between the box and Router, no HDMI signal link between the box and television (did you try a different HDMI cable on the two televisions ?).
Or the box could be attempting a software update (did you leave the box switched on for maybe 30 minutes to see if it can update).
If it was me, i would try a different HDMI cable between the box and television and then try another factory reset by pushing a small pin in the small reset hole on the back of the box (assuming you have the black NOW box) for around 30 seconds to see if something like a message pops up on the television screen like "Lets Get Started".
Should something show on the television screen when on the correct HDMI input source on the television, then follow the instructions on screen to setup the box again from scratch and when prompted use your existing NOW account details.
Other than that i am out of ideas.