i have TP plugs, not lamps, and if my plug stops working I notice the LED indicator not solid blue as it should be to indicate it is connected to home network, but rather blinking blue rapidly indicating it is trying to connect to the home network.
In other words, the plug has lost its wi-fi connection. There are reasons for this happening occasionally, and my plugs have an on/off switch that sometimes can fix this or just unplugging the plug for a moment helps it reconnect. If all these steps to reconnect don't help, then removing plug and plugging it in closer to better wi-fi signal gets it connected. Once good connection is made, plug can be removed and put back where it needs to be and it reconnects quickly.
So, the lamps must have similar LED indicators and also came with a card with quick instructions, so refer to that card (or find it at TP website).