Problem

You get a heap of errors similar to the following when trying to access different blades in Azure Portal

Error: Failed to retrieve the blade definition for 'VirtualMachinePropertiesBlade' from the server. self.importscripts failed

Cause

DNSFilter (or another DNS filter product) has blocked the domain.

Resolution

Open up your browser Developer tools (For Chrome Click the Three Dot menu, then More Tools, then Developer Tools or Press Ctrl + Shift + i ) and then view the Console tab

Check for the URL's of domains that are erroring out e.g.

https://afd-v2.hosting.portal.azure.net/iam/Content/Dynamic/qz_hE66gK6pN.js

Right click on the erroring URL and choose open in new tab. To confirm that it is DNSFilter causing the issue opening in a new tab should redirect you to a DNSFilter block page.

Once you confirm DNSFilter to be the issue log in to your DNSFilter Admin panel and add the domain to the Allow List. I put hosting.portal.azure.net NOT afd-v2.hosting.portal.azure.net. DNSFilter will ask you to add the CNAME's too. It's a good idea to accept this recommendation or you might still have issues.