Hi Hettervi,
I am the Product Owner and Developer for this App, the call out to the internet is just Splunk telemetry pull that you can opt-out which is part of the core product. The app does not need this to function. If you're in Chrome can you do an Inspect, Console and reload the main page that not loading. It will show the error if you can email or post it to the page where I can go ahead and help you with this issue.
One thing that might be causing this could be a caching issue on the upgrade of the app if you installed the original version which only supported 6.5 - 7.0. If you goto your Splunk URL path and use the following it should flush out the cache reference with http://localhost/en-US/_bump
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