The "Troubleshoot the Splunk App for Windows Infrastructure" topic actually discusses this, although pretty far down the document:
Dashboards fail to load after upgrading the app or Splunk
Enterprise If you experience an
issue where some dashboard panels or
menus fail to load after you upgrade
either Splunk Enterprise or the Splunk
App for Windows Infrastructure, clear
your web browser's cache, log out of
Splunk Enterprise, then log back in.
This should fix the problem.
This fixed my problem and I've gone on to configure the applications.
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