I have been trying to figure out what is causing 404 errors on one specific multisite I have on my VPS. Other multisite installations on the same VPS dont have this issue.
I can't really determine when after wich action this happened. Yesterday everything was working fine and now all the subsites under that multisite can't have any permalink structure then the default one (/?p=123) All the others will give an 404 error for all pages except the homepage.
I also have tried to find some solutions on the existing topics here related to a 404.
On the multisite I have Better Security and Wordfence installed, even with these diabled I still get the 404, with any permalink besides the default one.