This is my nextcloud log. Permissions are nginx:nginx on the /var/www folder and under. Also, the files exist, so I have no clue. (BTW, this is NextCloud 12, fresh install with NginX and MySQL)
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/vendor\/core.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: js\/core\/merged-template-prepend.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/search\/js\/search.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/js\/backgroundjobs.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: js\/core\/merged-share-backend.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/js\/jquery-ui-fixes.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/js\/files\/fileinfo.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/js\/files\/client.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/js\/contactsmenu.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/vendor\/jsTimezoneDetect\/jstz.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: js\/core\/merged-login.js, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/vendor\/select2\/select2.css, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/vendor\/jquery-ui\/themes\/base\/jquery-ui.css, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/css\/jquery.ocdialog.css, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}
{"reqId":"GfB8pPbR9nhp4eCo2eCN","level":3,"time":"2017-09-19T13:30:40+00:00","remoteAddr":"10.0.0.21","user":"--","app":"lib","method":"GET","url":"\/login?redirect_url=\/apps\/files\/","message":"ResourceLocator can not find a web root (root: \/var\/www\/hu.mycompany.cloud, file: core\/css\/guest.css, webRoot: , throw: false)","userAgent":"Mozilla\/5.0 (X11; Linux x86_64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/59.0.3071.109 Safari\/537.36","version":"13.0.0.3"}