@PankajG you may read this FAQ to troubleshoot, https://www.tp-link.com/support/faq/2965/. Or could you provide more detailed information of this problem?

@Inaty Was the power light keeping off when you use it for the first time or was it suddenly turn off while using? I think maybe you can check if the electricity supply is suitable for the power...

@Zooter39 you may check if your phone is connected to the WIFI signal of AC1750 rather than that of the front-end router. You can disconnect the WIFI first and move your phone close to the AC1750, to...