We're sorry you're having trouble. Can you please provide a little more information about the error you are seeing?
what apic-em sandbox lab are you working on ? it looks from the message that you haventh initiated the Discovery Scan on the APIC-EM controller. This is an standard message from the controller (and not an ERROR!) and it is telling you to initiate the Discovery of the network devices. Credentials and basic instructions are available in the getting started guide for the relevant lab and also more generic information about the functionality of the APIC-EM controller release are noted in the Release notes of the current APIC-EM...
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