Fix a 404 problem with CPT slug links on wordpress

Hello,

I’m experiencing a 404 error with my custom post type (CPT) “instituts”. My goal is to have URLs in the following format:
instituts/{slug parent}/{slug child}/{city}

However, when I click on the link, I get a 404 error.

I’ve tried:

Flushing rewrite rules (and using the after_switch_theme hook),
Adding custom rewrite rules,
Modifying the CPT registration (switching between hierarchical and non-hierarchical),
Adjusting my slug-building filter.
None of these approaches have resolved the issue. I need help from someone experienced in WordPress rewrite rules and CPT configuration to fix this problem.

Any guidance or suggestions would be greatly appreciated.

Thank you in advance!