Hello. I am experiencing the exact same problem.
I built my wordpress site and launched it and it worked fine until i enabled the jetpack plugin. then i kept getting 404 URL not found on this server error. so I deleted the site and rebuilt it because it wasn’t letting me log into the admin end.
I rebuilt it and launched it and got a comment that the site was not secure. most people viewed the site perfectly but one person said he was getting numerous alerts that the site wasnt safe and photos were not downloading. so I RE-ENABLED JETPACK to secure the site.
Now i have the 404 error all over again and even the people who could previously view the site, cant anymore. photos arent loading and on my end. I am unable to access the back end.
