Collabora is not working with Ubuntu 16.04 and Vesta CP

I cannot get Collabora to work with my system. Any ideas why? (I get Internal Server Error in Nextcloud)

I set it up in ‘/etc/apache2/sites-available/office.domain.xyz.conf’ and also in ‘/home/admin/conf/web/apache2.conf’ because of Vesta CP.

I followed up the official tutorial here: https://nextcloud.com/collaboraonline/

My virtual host config:

<VirtualHost 100.10.01.001:443>
ServerName office.domain.xyz:443

# SSL configuration, you may want to take the easy route instead and use Lets Encrypt!
SSLEngine on
SSLCertificateFile /etc/letsencrypt/live/office.domain.xyz/cert.pem
SSLCertificateChainFile /etc/letsencrypt/live/office.domain.xyz/chain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/office.domain.xyz/privkey.pem
SSLProtocol             all -SSLv2 -SSLv3
SSLCipherSuite ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GC$
SSLHonorCipherOrder     on

# Encoded slashes need to be allowed
AllowEncodedSlashes NoDecode

# Container uses a unique non-signed certificate
SSLProxyEngine On
SSLProxyVerify None
SSLProxyCheckPeerCN Off
SSLProxyCheckPeerName Off

# keep the host
ProxyPreserveHost On

# static html, js, images, etc. served from loolwsd
# loleaflet is the client part of LibreOffice Online
ProxyPass           /loleaflet https://127.0.0.1:9980/loleaflet retry=0
ProxyPassReverse    /loleaflet https://127.0.0.1:9980/loleaflet

# WOPI discovery URL
ProxyPass           /hosting/discovery https://127.0.0.1:9980/hosting/discovery retry=0
ProxyPassReverse    /hosting/discovery https://127.0.0.1:9980/hosting/discovery

# Main websocket
ProxyPassMatch "/lool/(.*)/ws$" wss://127.0.0.1:9980/lool/$1/ws nocanon

# Admin Console websocket
ProxyPass   /lool/adminws wss://127.0.0.1:9980/lool/adminws

# Download as, Fullscreen presentation and Image upload operations
ProxyPass           /lool https://127.0.0.1:9980/lool
ProxyPassReverse    /lool https://127.0.0.1:9980/lool
</VirtualHost>