@Chris Sarka, Thanks for posting in Q&A. Based on my researching, I find a similar issue with the same error as yours.
In that case, the issue was identified to be related to the Intune/Endpoint manager admin portal URL:
https://endpoint.microsoft.com
Works OK
https://devicemanagement.portal.azure.com
Does not work
Please check if we use the second URL to access Intune and add store new app. If yes, try to change to use the first one to see if it works. If there's any update, feel free to let us know.
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