So here is my case.
Yesterday I could still access XenCenter from Citrix Receiver. Then I needed to restart, but mistakenly restarted the server. Now when I try to access the Citrix Receiver with admin credential, here is what I get (previously I have some of apps that can be added by tapping + blade on the left):
Of course with this error, I can't access XenCenter console anymore to see what's wrong with the XenServer.
How I can access the XenCenter console again? I only know the IP Address of XenCenter and my Citrix Receiver.