S4048T, ipv6, static/default route not working

We are running 9.14(0.1) (though I've looked through all release notes since then and don't see anything relevant matching ipv6 or static). We have 4x of these switches running together and all ipv4 operation is working fine. I have plenty of ipv4 & ipv6 routing experience on other (most Cisco) platforms.

I have numerous interfaces with ipv6 configured and working as expected (all connected routes). The problem is when I try and connect to a neighboring Cisco ASA. 

I can't set a default route. This is working fine with IPv4, it is only with IPv6 I see the problem.

ipv6 route ::/0 tenGigabitethernet 1/48 fe80::
 

The command is accepted. However, the route does not show up in 'show ipv6 routes' (I see a note to this effect in the cli guide). I do see the cli output about gateway of last resort is not set. It does not show up in 'show ipv6 routes static' either. Both global and link-local addr of the Cisco are present in 'show ipv6 neighbors'. The interface is up. The LL addr is pingable when selecting the interface.

I have also tried using the global address of the next hop (vs the LL addr), no difference.

Independent of what the switch is reporting when I ping a connected addr from a host, it works correctly, and when I ping a device that would require the default route, it fails.

I assume I am doing something dumb. What am I missing?