Site Language Selector Doesn't Show

[artisticlight]

Jira: https://asfdaac.atlassian.net/browse/TOOL-2284

Note: The above link is accessible only to members of ASF.

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Describe the bug
The site language selector doesn't appear to allow the language to change when the yaml lists multiple languages.

To Reproduce
Steps to reproduce the behavior:
I created a branch of the Vertex docs at:

https://github.com/asfadmin/Discovery-asf-data-search-manual/tree/prod-new

This branch uses the mkdocs-asf-theme and the yaml contains navigation for English and Spanish but the language selected doesn't appear.

Expected behavior
I was expecting the language selector to appear. If I use the MkDocs Material theme and override the CSS to appear similar to the ASF theme then the selector appears and functions.

Additional context
Add any other context about the problem here.