@Yannick , thank you for the question.
Based on the question, I assume that you are using "Azure Automation Update Management" (please correct me if I am wrong). And your on-prem windows machine with DC (domain controller) role is no longer available in Azure Automation's Update Management view.
If the scenario above describes the issue that you are facing, please follow the steps as mentioned in this article - Machines don't show up in the portal under Update Management
This could mainly be related to machine not able to send data to LA workspace, quota limit or that the local configuration of the hybrid runbook worker is impacted. The link shared above contains detailed steps to perform the tests and re-install the hybrid worker, if required.
Hope this helps.
If the answer did not help, please add more context/further findings after following the steps above, and we will help you out. Else, if the answer helped, please click Accept answer so that it can help others in the community looking for help on similar topics.