Hello @Studmuffin 1134 ,
Thank you for posting here.
First
Do you request certificate on DC? If no, we can request certificate on DCs using Kerberos Authentication certificate template
or Domain Controller Authentication certificate template.
1.Type certlm.msc on Search Bar and click Enter.
2.Expand Certificates (Local Computer), right-click Personal, click All Tasks, and then click Request New Certificate.
In the Request Certificates page select Domain Controller Authentication
3.Check if that works for you!
Second
Check if the CA root certificate are install on both DCs and PCs (Trusted Root Certification Authority).
1.Type certlm.msc on Search Bar and click Enter.
2.Expand Certificates (Local Computer), click Trusted Root Certification Authority\Certificates.
Here is a similar case we can refer.
Smartcard Logon not enabled
https://social.technet.microsoft.com/Forums/windowsserver/en-US/ee52cb8f-c3cd-437f-9fc8-6884dd335394/smartcard-logon-not-enabled?forum=winserversecurity
If is does not work above, please confirm information below:
1.How many accounts have such issue?
2.How many machines have such issue?
Thank you for your understanding.
Best Regards,
Daisy Zhou