After deploying the new Cloud Proxy server and adding a vCenter for it to monitor, you are unable to create any Configuration Drift templates.
You go through the steps and the final step to "create" the template fails to build the template.
You have already reviewed KB 385509 and that does not appear to be the problem.
Aria Operations 8.18.x
vCenter 8.0.3 or later
The user account used in the vCenter integration for VMware Aria Operations does not have administrator privileges.
1. Access vSphere Client web UI as a user who has the privilege to view and edit the user accounts.
2. Click on the menu icon on the top left, then go to Administration > Single Sign On > Users and Groups.
3. Click on the Groups tab, then select Administrator. Then click on Edit to add the user/member to this Administrator group.
Refer to the KB article Troubleshooting VCF Configuration Drifts for additional insights that might uncover other anomalies.