@Roddyb sadly, the full reset, the full reset of the router nothing worked. Anyway TP-Link should not expect you to split Wi-Fi bands on routers - bad practice. today, 27 March, all my smart plugs...

Same thing happened to me, no physical changes so I am assuming software (6 x HS100 failed)

Try as I might, I cannot persuade my 6 HS100 to connect to my Wi-Fi. I would love to tell you I changed something but sadly I haven't. One morning they were all off-line and trying to rejoin them has...