"Failed to load resource" Splunk Add-on for ServiceNow 6.4

[sochase]

Just installed Splunk Add-on for ServiceNow 6.4 on Splunk Enterprise 8.X, and the app's ui is not responsive.  Just keeps showing "loading" (spinning). In Chrome Developer Tools, I see several 500s and 503s for things like
(Failed to load resource) /en-US/splunkd/__raw/servicesNS/nobody/Splunk_TA_snow/splunk_ta_snow_settings/logging?output_mode=json&_=1613605597716 

If I try to browse to the url that failed to load, I get the following error:

{"messages":[{"type":"ERROR","text":"Unable to xml-parse the following data: %s"}]}