If any of your TV's have a USB port on them rated at 900ma /0,9a then test the NOW Stick on them.
I would also try a different USB standard to USB micro cable if you have one around the house and maybe a 5VDC 1A or higher amp USB charger to see if the Stick low power message disappears.
I’m with @gavs82008 on this one.
If the stick says Low Power even when run with the supplied charger, then the charger, the cable, or the stick is faulty (assuming your mains hasn’t dropped to 180V, as happened to a work colleague of mine!).
So do a reset (with the stick plugged in and powered on, hold the little button on the side of it in for just over 15 seconds) and try it again.
If still no go, then try any any other USB charger you may have, with a USB Mini-connector cable for an Android device (they are all interchangeable), to eliminate these components from the problem.
If you still get the ‘Low Power’ message, then the stick is faulty 😢
But one of the above will hopefully fix it.