Real neon lights flicker due to the gasses settling, this isn't a defect, it's a common situation that can easily be resolved!
Neon and argon gasses are inserted into the glass tube by way of a vacuum. To create different neon colors, the inside of the tubes are lined with phosphorus powder. Occasionally - and especially after long periods of inactivity and/or storage in cold environments - the gasses can pool and settle in the powder, causing them to be unevenly dispersed in the tube.
The easiest way to get the juices flowing again is to carefully remove the glass tube from the base and give steady but gentle shake (be careful not to break the glass!) and then leave on for about 5-8 hours straight. If this does not resolve the flickering, you can follow our help guide here - How To Fix Partial Light or contact support.