Customer policy adopted injection via the reverse proxy of the Content Security Policy header for security reasons.
The policy adopted is basic: default-src 'self'
Opening the QlikView AccessPoint or Qlik Sense Hub may fail or the AccessPoint may only render partially.
The Browser Debug tools will provide more insight:

Environment:
QlikView
Qlik Sense Enterprise on Windows
The Header Content Security Option contains a string of rules that informs the browser which resource/code is trusted to be loaded, executed rendered.
More details on the argument could be found here:
https://www.w3.org/TR/CSP3/ ,
Resolution:
For QlikView Accesspoint a first example is to use Content-Security-Policy: "default-src 'self' 'unsafe-inline' data: ;" ; (note that using 'unsafe-inline' option could be unsafe in a the proxy injection scenario when the client will brose a different site , you could/evaluate to use instead the sha256-hashcode version )
Further option could be necessary if for example you have QlikView Extension Object ( Server and Document Extensions) that are using external resources downloaded from CDN locations;
In this case the troubleshoot is the same use F12/Development Tools to check the resource that violates the policy and ad an exclusion.
Related Content:
QlikView Access Point Shows "Loading Content" Indefinitely,
What is CSP (Content-Security-Policy) and How does it Relate to Qlik?