My Posts don't load

Have you tried to resave permalink settings under Settings >> Permalinks?

Yes I have changed my permalinks settings, but the problem is still there.
The fact is I don’t really know if it is a permalinks problem…

After you make the change, is your .htaccess file getting updated?

Where can I find my .htaccess file?
I log in FileZilla and then, where can I find it?

Some posts of mine load after having changed permalinks, other (the majority of them) don’t… So, I don’t know if it is a permalink problem…

this is my site https://www.fondazionenovarese.it

this is one of my posts that load https://www.fondazionenovarese.it/bando-emblematici-maggiori-2015-risultati/

this is one that doesn’t https://www.fondazionenovarese.it/bando-congiunto-fcn-nuares-2015-risultati/

the htaccess file is usually in the main wordpress directory

My site run on Nginx, there’s no .htaccess file (or so they told me).
There is nginx.config.
So, in there anyone who can tell me how to config yoast on Nginx.
Thank you.

Yoast does not write to the htaccess. I do not believe that the posts not loading has much if anything to do with Yoast being installed. I think it has to do with the permalink settings not being saved correctly to the nginx.config this article should help you fix the permalink issues.