I am trying to connect two new Echo dots together in a group. Both are connected to the same WiFi both at 2.4GHz and all credentials are the same. Alexa is unable to sync the two speaker and if I try to select the speakers for the group separately as soon as I select speaker 1 it blanks out speaker 2 and vice versa showing Network error. I have tried EVERYTHING to resolve but cannot get them to group together... any advice please. Many thanks.