New Access Token error, "Error: unable to get local issuer certificate"

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API newbie here. I'm taking the Learn Postman With Paul course. I'm at the Get Initial Token phase in Postman. I've filled in all my fields, clicked "Get New Access Token", and I get prompted to sign in... Which I do - but then I get the, "Error: unable to get local issuer certificate" error. What am I missing?