No electric power, completely dead, good battery
Pardon me but how do you know the battery is “good”? Have you had it tested?
Newish batteries can and do fail or the alternator could be bad, which would drain the battery. If the battery is in fact good, the next suspect would be the cables. Make sure they’re securely connected, in good condition, and that there’s no corrosion. Check the fusible links in the cables to make sure they haven’t blown.
Assuming the battery connections have already been checked okay you then need to check how power gets to the main electrical panel under the hood. The connection to it from the battery may be bad. Also check the main grounding to the engine and chassis for any problems. You should have at least a test light probe to check for voltage with.