Is this on the Always On APIC Sandbox? AT https://sandboxapicdc.cisco.com/? If so I just looked and it's up and running.
This sandbox is monitored and when there are problems it is automatically reset, however that processs can take a few minutes. Your error message looks like you caught it during a reset time, unfortunate but it does happen. Try it again and see if you are good now.
Hank
