[BlueOnyx:21182] Bind on 5209R not accepting queries

[Colin Jack]

After some ideas please.

The server that holds the master zone for our domain has stopped accepting queries (SERVFAIL):

C:\Users\Colin.MAINLINE>dig @iris.mainline.co.uk cloud.mainline.co.uk

; <<>> DiG 9.3.2 <<>> @iris.mainline.co.uk cloud.mainline.co.uk
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 122
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;cloud.mainline.co.uk.          IN      A

;; Query time: 133 msec
;; SERVER: 208.77.146.130#53(208.77.146.130)
;; WHEN: Mon Jul 17 12:36:15 2017
;; MSG SIZE  rcvd: 38

I have disabled/saved/enabled/saved restarted 'Allow queries from Everyone' in the DNS GUI.
Restarted named-chroot.
I have even restarted the server.

Desperate for ideas please.

Thanks

Colin