There could be multiple things that can lead to this issue, let's go through them 1 by 1.
1. Make sure your workstation is properly cooled. Overheating can lead to performance throttling.
2. If you are using Windows 10 then upgrade to Windows 11 as this seems to have fixed this issue in the past, see this article for more information:
https://support.chaos.com/hc/en-us/articles/5411622662289-Lower-CPU-utilization-with-Intel-Alder-Lake-processors3. If you are using any kind of virtualization (VMware, Microsoft Server, etc.) then make sure your administrator has not limited your hardware usage.
4. Check if this is happening only with Corona and working fine with other render engines such as V-Ray.
5. Check if this issue is scene specific i.e., only happening with this scene and does not happen on other scenes.
6. Check if your workstation is not set to power-saving mode and is set to utilize full performance.
Once you do all this, please let me know about your findings.