Whitelist/Blacklist error

I’ve switched from lighttpd to nginx and now when I click on Whitelist link ou Blacklist and I have an error.
Same when I try to whitelist or blacklist a domain.

Expected Behaviour:

Display the list and/or add the domain to the list

Actual Behaviour:

Error saying:
Failure! Something went wrong, see output below:

(and there is no output)

Debug Token:

https://tricorder.pi-hole.net/11jideurh3

nginx is not supported as a Pi-hole web interface. There is an unsupported community guide you can try, or you can run nginx and lighttpd on different ports.

https://docs.pi-hole.net/guides/nginx-configuration/

Thank you jfb for your input. That page didn’t really help to understand the underlying problem.
The whole website works without a problem, only the Whitelist/BlackList menu on the left.
How/where can I track the error the loading of that page produces ?
That will help me understand how I can fix it.