GU43TU8079U - ALEXA/GOOGLE/BIXBY only work when WiFi 2.4 connected

[sevegee]

Hi,

Strange... if I connect the TV either wired or to the 5GHz WiFi then none of the voice assist options work.
(msg " cannot connect to Alexa server" - same with the other services)

All work when connected to 2.4GHz WiFi - what's happening