What does Serious delinquency mean on a refused credit application/report?

What does Serious delinquency mean on a refused credit application/report?
Added (1). I am 24 and have only applied for a tjmxx credit card before years ago, that's the only thing. I have zero student loans, zero debt, no mortgages, and always pay my stuff on time and have over 5,000 in my checkings account. Any help?

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