Certificate renewal on Ubuntu 16.4 failed

[_az]

Perhaps read over this: What you need to know about TLS-SNI validation issues

Once you have upgraded Certbot as in the above post, perhaps then try:

certbot renew --preferred-challenges http

@Pillarator

The nextcloud instance is not issued on the standard ssl 443 port but on 59something which is forwarded to the server but after the first activation failures i also forwarded the ports 80 and 443 as an attempt to fix the problem

You'll also need to make sure that your Apache server that Certbot is creating a certificate for is accessible on port 80. At the moment your Fritzbox control panel appears to be on that port instead.