cbas/analytics/link REST API unauthorized in mixed cluster

I created a mixed cluster with 6.6.1 (in Vagrant) and a local build of 7.0.

When I connect to the UI on the 7.0 node, if I go to the Analytics section, the code requests info about links on /_p/cbas/analytics/link, which returns an HTTP 401 error, which forces the UI to reload. This REST endpoint is used in both 6.6 and 7.0, so I don't know why it wouldn't work in a mixed cluster. I'm logged in as Administrator.

From the http_access.log:

::1 - Administrator/UI [25/Apr/2021:13:05:49 -0700] "GET /_p/cbas/analytics/link HTTP/1.1" 401 chunked "http://localhost:9091/ui/index.html" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/89.0.4389.128 Safari/537.36" 1222