Hi,
If you have recently applied .Net updates on your Microsoft Windows server, it may break "Web sites" section in your SolidCP. SolidCP has yet not releases official update but there is a work around to fix this issue. It requires to edit your portal's web.config file to apply workaround. For more details, you can refer our KB on
SolidCP Error in Web Sites section after Windows updates.
- Kailash