When installing a new Oracle 12c and later agent on Windows:
- where the listener is already installed,
- the Oracle service is running, and
- you are using a standard Oracle home user who is not part of Admin group;
be sure to allow full access to Oracle home user on the Precise root directory on the monitored machine (the machine where oracle agent is being installed/oracle instance is running), and add the Oracle home user to the performance monitoring group.