the apic-em EFT2 Always on sandbox is being deprecated. however, for now i would suggest reserving an APIC-EM GA 1.1 sandbox if you would like to have full access to an APIC-EM server instance. The Always on sandbox labs are really for basic testing from an REST based perspective and not usually accessed via the UI.
Asan FYI, the UI is Topology UI is responding as expected. I would check contention on your internet link and if its still an issue I can check the EFT2 Always On service for you further.