Might this be the real error logged by Webinoly log?
2019/11/22 23:08:46 [crit] 52446#52446: *18154 pread() "/etc/nginx/" failed (21: Is a directory), client: 158.174.228.32, server: domain.se, request: "GET /wp-admin/ HTTP/1.1", host: "domain.se"
Command nginx -t tells me /etc/nginx/nginx.conf is both syntax ok and test is successful.