Why does my Page Preview/Version Preview or Accessible review tab not work and keep loading when in designer?

If Single Sign-On (SSO) or Reader Login security rule is your applied security rule, preview features such as Page Preview, Version Preview and Accessibility may not load correctly.

This happens because the system attempts to display a login screen, which cannot be rendered in preview mode.

How can I fix this?
We advise to temporarily change your security settings (don't worry - as its unpublished it won't affect the security of your document)

Change the security rule to “Disable Search Engines.”
Save your changes.
Reopen designer and click 'Page Preview/Version Preview' — it should now work as expected.

Important:
Once you’ve finished designing, remember to revert the security rule back to its original setting before publishing.