Can't open my nextcloud website

Nextcloud version :12.0.4.3
Operating system and version :Debian 9
nginx version : nginx/1.10.3
PHP version :PHP 7.0.27

The issue you are facing:I can’t open my nextcloud website.However,I can use my android app to upload files and sync files use the desktop app.

Is this the first time you’ve seen this error? Y

The output of your config.php file in /path/to/nextcloud

<?php
$CONFIG = array (
  'instanceid' => 'ocid',
  'passwordsalt' => 'mysalt',
  'secret' => 'mysecret',
  'trusted_domains' =>
  array (
    0 => 'cloud.mydomain.com',
  ),
  'datadirectory' => '/var/www/nextcloud/data',
  'overwrite.cli.url' => 'https://cloud.mydomain.com',
  'dbtype' => 'mysql',
  'version' => '12.0.4.3',
  'dbname' => 'NextCloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'myname',
  'dbpassword' => 'mypasswd',
  'installed' => true,
  'memcache.local' => '\OC\Memcache\APCu',
);

The output of your nginx in /var/log/nginx/error.log:

2018/02/04 10:06:27 [crit] 23097#23097: *110204 SSL_do_handshake() failed (SSL: error:1417D18C:SSL routines:tls_process_client_hello:version too low) while SSL handshaking, client: x.x.x.x, server: 0.0.0.0:443
2018/02/04 15:53:20 [error] 23097#23097: *110287 connect() failed (111: Connection refused) while connecting to upstream, client: 121.230.x.x, server: cloud.mydomain.com, request: "PROPFIND /remote.php/webdav/ HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "cloud.mydomain.com"
2018/02/04 15:55:10 [error] 23097#23097: *110306 connect() failed (111: Connection refused) while connecting to upstream, client: 121.230.x.x, server: cloud.mydomain.com, request: "GET /remote.php/dav/files/toptyloo/InstantUpload/Camera/2018/01/IMG_20180128_153755.jpg HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "cloud.mydomain.com"
2018/02/04 15:56:01 [error] 23097#23097: *110294 connect() failed (111: Connection refused) while connecting to upstream, client: 121.230.x.x, server: cloud.mydomain.com, request: "GET /remote.php/dav/files/toptyloo/InstantUpload/Camera/2018/01/IMG_20180131_203651.jpg HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "cloud.mydomain.com"

This related to an openssl problem.

do ( i am using letsencrypt, modify to check your config )

echo quit | openssl s_client -connect yourwebsite:443 -CAfile /etc/letsencryp t/live/mywebsite/cert.pem

you will get

Peer signing digest: SHA512
Server Temp Key: ECDH, P-256, 256 bits
---
SSL handshake has read 3664 bytes and written 302 bytes
Verification error: unable to get local issuer certificate
---
New, TLSv1.2, Cipher is ECDHE-RSA-AES128-GCM-SHA256
Server public key is 4096 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : ECDHE-RSA-AES128-GCM-SHA256
    Session-ID: B6190A2A1675CAFC40F8071AD7BD3407C1EF2C3851DC8140A720CE0E486ED9E0
    Session-ID-ctx:
    Master-Key: C9125096609D64875FBA8986C2303283F5159491557CAE82D3DB6CB855ECC7527EBEDF6332AFFA50BDF8BCE2A6CCD2F6
    PSK identity: None
    PSK identity hint: None
    SRP username: None

You need to be TLSv1.2

It has been TLSv2 already but it doesn’t work.

re-reading your original post, seem you Have nextcloud working but no web interface RIGHT ??

looks more like an vhost apache problem could you pass your apache config for your host.

I think I am not using apache and the apache log files are blank.

In that case, this is why you can use nextcloud.

You need to create a vhost in apache2 for nextcloud. Or you need to install nextcloud in your www root.
For debian, this www root is /var/www/html