I have struggled with the same issue as you mention above with a Samsung soundbar HW-Q70R. I have tried everything such as unplug the soundbar from the socket, reset the soundbar, I made a hotspot via mobile phone, nevertheless all the time I was not able to connect the soundbar to wifi. I used my Samsung Galaxy S9 and Ipad 8th generation. I am using WIFI mesh from TP-LINK. Today, I finally connected my soundbar to my WIFI network. I used our old iPhone SE and the connection was successful via 20 seconds. Frankly speaking, I think that the problem was with my new devices, for a successful connection you have to use your old devices which mainly using wifi 2,4 GHz. I hope that will help you.