@heshamk: can you please provide which browser do you use to enter the web interface of the VCN ?
Did you clear cookies from the browser ? please try again connecting after clearing the cookies and use the Internet Explorer for this and let us know if you have the same issue after.
If the error is still present, can you please check if all services are working properly: Choose System Management > Business operation and management
If needed, you could restart the
OMU service.