Unable to only allow TLS 1.3

[ksb749]

I use NPM on a domain, which works greatly, but now i want higher security, so i only wanna allow TLS 1.3.
I have that on another nginx server, but just not with NPM as manager.

I login > click hosts > click proxy hosts > click options next to the domain > select edit > click Advanced and add:

ssl_protocols TLSv1.3;
ssl_prefer_server_ciphers off;

But, the domain is now down.. I can renew the SSL in NPM, but why cant i set it to only use TLS 1.3?

When i do a:
openssl s_client -connect example.com:443

It tells both 1.2 and 1.3 is there.