Unable to access web interface, no output from OCC but app access functional

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Nextcloud version (18.0.6):
Operating system and version (Ubuntu 16.04):
Apache or nginx version (Apache/2.4.18 (Ubuntu)):
PHP version ( PHP Version 7.3.19-1+ubuntu16.04.1+deb.sury.org+1):

Following a server reboot (I think) yesterday, I am receiving “HTTP Error 500” when I try to access the web interface of my Nextcloud installation.
I tried digging around a little but I hadn’t had any updates related to web services/php etc for quite a while before it. I tried disabling the php mod in apache and got the expected wall of text when trying to visit my Nextcloud address, I downloaded php7.4 and got the same result - blank screen in Firefox, HTTP 500 error in Chrome.
I was working last night so I didn’t dig too much further.

I did recall a couple of app updates recently to Nextcloud, but unfortunately until last night, I didn’t have logging enabled (I had the file set in the config but didn’t have the rest of the logging entries set)
Today, I’ve tried using OCC commands to see if it could shed any light on the situation and even they aren’t working. ANy command I run just ends with no output to the terminal and no errors, though it isn’t immediate, there are maybe 4-5 seconds between me issuing the command and being returned to the terminal. This is being carried out over SSH as it’s a headless server, but I’ve used OCC before multiple times…

My Nextcloud apps on my phones/PC ARE working and syncing data, but on my PC (Manjaro Linux) I’ve noticed the app can’t tell me how much space is being used. So it seems at least some of the back end is still working, but something had happened to the front end UIs.

Is this the first time you’ve seen this error? (Y/N): Yes

Steps to replicate it:

  1. Currently unkown

The output of your Nextcloud log in Admin > Logging:

https://pastebin.com/7jDNUCtM

Those are log entries of me running an occ staus, then occ app:list (as I noticed an entry regarding the mail app, I was going to disable it to see if it made any difference)
Then I tried to access the web interface just prior to capturing the log.

I think there were some entries in the middle of my phone trying to upload pictures.

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

<?php
$CONFIG = array (
  'instanceid' => 'ocvfp7g5olni',
  'passwordsalt' => 'txYQTE2k5t4SRF/qoQ6FIHS6GRDtN9',
  'secret' => 'FttHt2kr/9yV15mxCvT3v1e2nTF6OfRPt0xcCdBy5Q+wN7Ev',
  'trusted_domains' => 
  array (
    0 => '1',
    1 => 'ubuntuserver',
    2 => 'ubuntuserver.local.ftb',
    3 => 'nextcloud.ubuntuserver.local.ftb',
    4 => 'nextcloud.ubuntuserver.ftb',
    5 => '10',
    6 => '',
    7 => '',
    8 => '',
  ),
  'datadirectory' => '/willzpool/nextcloud/data',
  'overwrite.cli.url' => '',
  'dbtype' => 'mysql',
  'version' => '18.0.6.0',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'nextcloud',
  'dbpassword' => '',
  'logtimezone' => 'UTC',
  'installed' => true,
  'mail_smtpmode' => 'smtp',
  'mail_smtpsecure' => 'tls',
  'mail_from_address' => '',
  'mail_domain' => '.com',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_smtpauth' => 1,
  'mail_smtphost' => 'smtp.gmail.com',
  'mail_smtpport' => '587',
  'mail_smtpname' => '@gmail.com',
  'mail_smtppassword' => ';',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'maintenance' => false,
  'theme' => '',
#  'loglevel' => 2,
  'updater.release.channel' => 'stable',
  'mysql.utf8mb4' => true,
#  'logfile' => '/var/log/nextcloud/nextcloud.log',
"log_type" => "file",
"logfile" => "/var/log/nextcloud.log",
'logfilemode' => 0640,
"loglevel" => "0",
"logdateformat" => "F d, Y H:i:s", 
);






The output of your Apache/nginx/system log in /var/log/____:

PASTE HERE

There have been no errors in the error log for any attempts to access NExtcloud either last night or today.

Please let me know if any of the other logs in my Apache folder may be of help,

Ok, well I solved my own problem with brute force and ignorance.

I was still unsure about the mail app errors, so since I couldn’t do anything with OCC I just moved the mail folder out of the apps folder and hey presto, everything worked again. I even got brave and installed it again and all was good, it must have been corrupted during an update.