Configuring IPv6 on a dedicated server under Ubuntu 20.04.1 LTS with systemd

I have a dedicated server with OVH. It has multiple IPv4 addresses, and a /64 IPv6 assigned.
The IPv4 works fine - but I can only seem to access the first IP in the range for IPv6. Any attempt to access anything after 0 within the /64 fails.

I've tried https://docs.ovh.com/ca/en/dedicated/network-ipv6/ and feel I'm missing something.

My config looks like this rn:

root@daserver:/etc/systemd/network# pwd
/etc/systemd/network
root@daserver:/etc/systemd/network# grep -n . *
50-default.network:1:# This file sets the IP configuration of the primary (public) network device.
50-default.network:2:# You can also see this as "OSI Layer 3" config.
50-default.network:3:# It was created by the OVH installer, please be careful with modifications.
50-default.network:4:# Documentation: man systemd.network or
50-default.network:6:[Match]
50-default.network:7:MACAddress=
50-default.network:9:[Network]
50-default.network:10:Description=network interface on public network, with default route
50-default.network:11:DHCP=no
50-default.network:12:Address=/24
50-default.network:13:Gateway=
50-default.network:14:#IPv6AcceptRA=false
50-default.network:15:NTP=ntp.ovh.net
50-default.network:16:DNS=127.0.0.1
50-default.network:17:DNS=213.186.33.99
50-default.network:18:DNS=2001:41d0:3:163::1
50-default.network:19:Gateway=ff:ff:ff:ff:ff
50-default.network:20:Destination=ff:ff:ff:ff:ff
50-default.network:22:[Address]
50-default.network:23:Address=83::/64
50-default.network:25:[Address]
50-default.network:26:Address=/32
50-default.network:28:[Route]
50-default.network:29:Destination=ff:ff:ff:ff:ff
50-default.network:30:Scope=link
50-public-interface.link:1:# This file configures the relation between network device and device name.
50-public-interface.link:2:# You can also see this as "OSI Layer 2" config.
50-public-interface.link:3:# It was created by the OVH installer, please be careful with modifications.
50-public-interface.link:4:# Documentation: man systemd.link or
50-public-interface.link:6:[Match]
50-public-interface.link:7:MACAddress=
50-public-interface.link:9:[Link]
50-public-interface.link:10:Description=network interface on public network, with default route
50-public-interface.link:11:MACAddressPolicy=persistent
50-public-interface.link:12:NamePolicy=kernel database onboard slot path mac
50-public-interface.link:13:#Name=eth0 # name under which this interface is known under OVH rescue system
50-public-interface.link:14:#Name=eno3 # name under which this interface is probably known by systemd

Any ideas on how I can have the server listen to things on IPs within the /64 other than the first IP? I assume I have to make the server a router on the first IP for the remainder of the range.