Just purchased three Deco M9Plus, they are connected in "Access Point" mode and the master deco is wired to my Drayton router.

everything connects fine, with the exception of my company MacBook Pro.

I have turned on guest WiFi and enabled in 2.4ghz only and later tried 5ghz only, along with isolating from rest of the network. Fast roaming is disabled.

Mac Book connects to WiFi SSID and I can ping both the router and the bbc.co.uk (however the ping drops connection frequently).

Also no other network services are working for example:

However when I try to open Chrome or Safari browser I get an error that the server is not responding.

Opening outlook it is unable to connect to server.

Trying to connect to VPN client, the address is unable to resolve. 
 

it's as if the MAC is completely disconnected. on the odd occasion the browser connects it is really, really slow to load the webpage (3-4mins to load the whole page), it's completely intermittent.

All other devices connect without issue (iPads, iPhones, IOT devices, windows laptop) no issues at all, so I know it's not a WAN issue.

apple wireless diagnostics reports the following:

Crowded WiFi channel - recommends using 5Ghz, although I already have this set to 5ghz only.

Conflicting country codes - Deco is using DE and MAC is using Automatic

Cusom DNS settings - network config is not using router DNS (it is using 8.8.4.4 on both router and MAC)

im lost I can't get it working at all, or then it connects works for a few hours and then loses connection and I have no ability to get connected for hours, then it strangely just works again.