Smart plug Hs 103 not connecting to Nokia G-2425G-A router. I had once successfully connected it but now its not connecting. I usually have around 10 devices connected.

Its a dual band router and my phone's WIFI shows the 2.4 GHz SSID but while resetting and setting up the plug, it doesn't show the 2.4GHz SSID. Even manually entering the details, it tries to connect but gets stuck. How can the problem be solved?