IPv6 ping failing to IPv6 – Range. SLAAC address pings fine.

This Linode has been operating since December 2018, although not with IPv6 at that time.
IPv6 was later added with 2 Addresses.
1 via SLAAC.
1 via an attached /64 network.
Recently the IP Address in the attached /64 network failed. The SLAAC IP Address is still working fine.
This is the failure message from another Linode in a different Data Centre.

ping6 -c 4 2600:3c00:beef:beef::3274:128f
PING 2600:3c00:beef:beef::3274:128f(2600:3c00:beef:beef::3274:128f) 56 data bytes

From 2600:3c0f:2:32::2 icmp_seq=1 Time exceeded: Hop limit
From 2600:3c0f:2:32::2 icmp_seq=2 Time exceeded: Hop limit
From 2600:3c0f:2:32::2 icmp_seq=3 Time exceeded: Hop limit
From 2600:3c0f:2:32::2 icmp_seq=4 Time exceeded: Hop limit

--- 2600:3c00:beef:beef::3274:128f ping statistics ---
4 packets transmitted, 0 received, +4 errors, 100% packet loss, time 3005ms

All help appreciated.