If 95% of HIV Cases test Positive within 30 days.....?

If 95% of HIV cases seroconvert (produce antibodies) within 30 days.. What causes the remaining few to take up to 3 months and even fewer up to 6 months? Would a much longer Seroconversion mean a stronger or weaker immune system or what? Intersted hereIf 95% of HIV Cases test Positive within 30 days.....?
Sometimes people with a weaker immune system PRIOR to infection (due to cancer, chemotherapy, radiation, organ transplant anti-rejection drugs, or autoimmune issues) can take longer to produce antibodies to HIV once they are infected. A stronger immune system would produce the antibodies faster.