BGP Failing with "error code 6 subcode 5 (Connection rejected)"

Morning all.

Ive just installing a Zywall 310 (Firmware Version:V4.71(AAAB.0) / 2022-02-22 20:44:02)

I have a interface connected to a network where there are two BGP neighbors. I have ping connectivity to them both.

Diags >

Router# show bgp summary
Neighbor        AS          MsgRcvd  MsgSent  TblVer   InQ    OutQ   Up/Down   State/PfxRcd
===============================================================================
172.xxx     65001       10       5        0        0      0      never     Idle
172.xxx     65001       12       6        0        0      0      never     Idle

Ive tried changing few things on the 310 but still the same.

Doing a packet capture i see im getting this from both neighbors >>

Border Gateway Protocol - OPEN Message

Type: NOTIFICATION Message (3)

Major error Code: Cease (6)

Minor error Code (Cease): Connection Rejected (5)

Searching the web i only find this > https://knowledgebase.paloaltonetworks.com/KCSArticleDetail?id=kA10g000000ClhtCAC

Any pointers / Suggestions please?

Thanks in advance