@Chris Phillips Thanks for your patience on this.
I am summarizing the discussion and posting it as answer for the benefit of community.
Upon deeper investigations, our engineering team has identified a bug, and a fix has been deployed as well.
Customer has retried the installation operation and confirmed that they are able to perform installations on notification hub.
Please accept as Yes if the answer provided is useful, so that you can help others in the community looking for remediation for similar issues.