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Sorry to hear you’re facing problems 
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In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 12.0.2): 12.0.0.19
Operating system and version (eg, Ubuntu 17.04): Ubuntu 18.04.1
Apache or nginx version (eg, Apache 2.4.25): 2.4.29
PHP version (eg, 7.1):7.2.7
The issue you are facing: After upgrade 13 → 14.0.0.19 (forbidden 403, apps/files/)
Is this the first time you’ve seen this error? (Y/N): Yes
Steps to replicate it:
The output of your Nextcloud log in Admin > Logging: I can’t login
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
The output of your Apache/nginx/system log in /var/log/____:
Apache error.log
Cannot serve directory /var/www/nextcloud/apps/files/: No matching DirectoryIndex (index.php,index.html) found, and server-generated directory index forbidden by Options directive, referer: https://xxxxxx.xxx/index.php/login
Apache access.log
IP-adresss - - [16/Sep/2018:06:17:28 +0200] "GET /apps/files/ HTTP/1.1" 403 4320 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko"
Apache nextcloud.conf
<FilesMatch “.(cgi|shtml|phtml|php)$”>
SSLOptions +StdEnvVars
Alias /nextcloud “/var/www/nextcloud/”
<Directory /var/www/nextcloud/>
Options +FollowSymlinks
AllowOverride All
SetEnv HOME /var/www/nextcloud
SetEnv HTTP_HOME /var/www/nextcloud
.htaccess
IfModule mod_dir.c
DirectoryIndex index.php index.html
/IfModule
#!/bin/bash
ncpath=’/var/www/nextcloud’
htuser=‘www-data’
htgroup=‘www-data’
rootuser=‘root’
#printf “Creating possible missing Directories\n”
#mkdir -p $ncpath/data
#mkdir -p $ncpath/assets
#mkdir -p $ncpath/updater
printf “chmod Files and Directories\n”
find ${ncpath}/ -type f -print0 | xargs -0 chmod 0640
find ${ncpath}/ -type d -print0 | xargs -0 chmod 0750
printf “chown Directories\n”
chown -R ${rootuser}:${htgroup} ${ncpath}
chown -R ${htuser}:${htgroup} ${ncpath}/apps/
chown -R ${htuser}:${htgroup} ${ncpath}/core/
chown -R ${htuser}:${htgroup} ${ncpath}/config/
chown -R ${htuser}:${htgroup} ${ncpath}/data/
chown -R ${htuser}:${htgroup} ${ncpath}/themes/
chown -R ${htuser}:${htgroup} ${ncpath}/updater/
chmod +x ${ncpath}/occ
printf “chmod/chown .htaccess\n”
if [ -f ${ncpath}/.htaccess ]
then
chmod 0644 ${ncpath}/.htaccess
chown ${rootuser}:${htgroup} ${ncpath}/.htaccess
fi
if [ -f ${ncpath}/data/.htaccess ]
then
chmod 0644 ${ncpath}/data/.htaccess
chown ${rootuser}:${htgroup} ${ncpath}/data/.htaccess
fi