By replacing the entire ui folder with your old custom UI, you broke the new UI components used by Rapid Setup and Access Reviews in 8.5 which is why you’re seeing blank pages.
In 8.5, SailPoint introduced UI changes and updated JavaScript dependencies (especially for Rapid Setup and Access Reviews). Replacing the entire ui folder with the 8.4 version breaks those pages, which results in a blank screen.
What to do:
8.4 custom UI is not backward‑compatible with 8.5
Rapid Setup and Access Review pages rely on new UI components
Overwriting the full ui folder is unsupported in 8.5
Recommended fix:
Restore the original 8.5 ui folder
Re‑apply your customizations selectively (CSS, branding, specific overrides only)
Do not replace core UI files
Clear browser cache and restart the app server after changes