@TP-Link_Deco Hi, so sorry for not replying I didn't receive a notification to say I'd received a response. Thanks for getting back to me, but strangely the problem seems to have resolved itself...

Hi, I have recently setup three P9 deco units to provide WiFi coverage in the house and a cabin in the garden. The main unit in the house is connected to the ISP modem with other unit in the house...