Hello Valentinus Fao,
Thank you for posting in Microsoft Community forum.
Based on my knowledge, certificate template is stored on Domain Controller in AD.
1.Please ensure your Domain Controllers in the domain are online and running.
2.You can try to check if you can ping the domain and IP of the DC and FQDN of the domain on CA server.
For example:
If you domain name is a.com and the IP of the domain is 1.1.1.1 and the name of Domain controller is DC (if your DC is also a DNS server).
ping a.com
ping 1.1.1.1
ping DC.a.com
3.Check if your CA server can communicate to Domain and Domain Controllers.
I hope the information above is helpful.
If you have any question or concern, please feel free to let us know.
Best Regards,
Daisy Zhou