Hi @KdB,
do you have cloudflare? The ACME howto is intended to use it with cloudflare. If you don’t have cloudflare, a solution to get back to defaults is in the howto thread:
The certificates are defined in /etc/httpd/conf.d/ssl.conf for apache and in /etc/nginx/conf.d/onlyoffice-documentserver.conf for nginx.
These are the commands to set the certificate in nginx from the onlyoffice howto:
# add ssl cert config - change if using letsencrypt or own certs
sed -i 's!{{SSL_CERTIFICATE_PATH}}!/etc/pki/tls/certs/localhost.crt!' /etc/nginx/conf.d/onlyoffice-documentserver.conf
# add ssl key config - change if using letsencrypt or own certs
sed -i 's!{{SSL_KEY_PATH}}!/etc/pki/tls/private/localhost.key!' /etc/nginx/conf.d/onlyoffice-documentserver.conf