Have you rebooted the phone? Go ahead and reboot your router too.

iphone rebooted, no change. 

Why would Router reboot work? All other devices work.

This iPhone is connected to wifi via manual IP address, would that matter?

Why on earth would one do that, in this day and age? It’s asking for trouble, including potential IP conflict. Manually configured IPs still have their place for infrastructure components, but not for client stations especially a mobile. If you want to fix IPs then use reservation in the DHCP server.

its because i have other issues between 2 routers which are 100m apart and i cant get the problem solved. Im going through numerous suggested fixes and one was to use manual/Fixed IPs. Im not a network expert so im figuring this out.

iv applied a static IP from BT Router to this phone. Do you say it then shouldnt be set to manual on the phone itself?

Presumably you have two routers to provide sufficient WiFi coverage, and one is cascaded off the other via an Ethernet connection. I take it that the BT router is the main one. In that case the second router needs to be switched to access point mode (sometimes called bridge mode), otherwise it will set up a different IP subnet. Sonos controllers and players should all be on the same subnet.

Many modern routers have an explicit config option for access point mode. If not, you can follow the advice here: https://www.cnet.com/home/internet/how-to-turn-an-old-wi-fi-router-into-an-access-point/

As for your specific query, if the IP is reserved in the BT router then the phone itself should be set to use DHCP (the default network configuration).

Your first point; yes, all seems set up correctly. In my limited knowledge fo doing this, ive done it in several houes and its always worked. 192.168.1.254 and 253 are the routers, DHCP is 50 to 250, 1-49 reserved.

Phone has a reserved IP, changed phone back to ‘Automatic’ and i can now login..

Thank you for guidance.

Doesnt sort the fact that devices fall off the second 253 router, and need auth from first router for some reason, but thats another forum.:)

How do you mean: “fall off”? Do they simply disconnect on their own, or is there a problem when roaming between the two routers?

Many mobile devices won’t roam unassisted (i.e. without centrally managed handoff) unless the access points share the exact same credentials -- security/encryption (e.g. WPA2+AES) and SSID/password -- as well as the same channel.

some devices stop working on the second router and then self assign themselves an IP address which is nothing to do with my network. Others dont and are fine.

The main culprit is a new MacBook Pro.

Both routers have exact same security/encryption, SSID, password, but i was advised they should have different channels.

The 2 routers are 100m apart so i guess wouldnt overlap/mesh/onstruct each other

Strange. Is there a VPN involved at all? You could try and ascertain whether the device is still connected to the router’s BSSID. If the MacBook can’t tell you, the router almost certainly can.