This is normal and not a sign of misuse. Blackheads form when excess sebum mixes with dead skin cells inside the pore opening and becomes oxidized. Your skin produces oil continuously, and the cells at the pore surface shed throughout the day. A nose strip can lift out some of the loose material at that moment, but it does not switch off sebum production or change the rate at which your skin cells turn over. Because of that, the pore fills up again and the blackhead becomes visible again after days or weeks.
Humid weather and daytime shine can make the problem more noticeable. That is why the product works best as an occasional extra step to tidy the nose before makeup or after a long week, not as a standalone solution. If you want longer-lasting visible results, the practical approach is a routine that keeps the area gently clean on most days: a mild cleanser, leave-on products that help keep pores clear, and a moisturizer labelled non-comedogenic if your skin tolerates it.
Some people see a bigger difference when they combine the strip with a leave-on pore-care product rather than using the strip alone. The strip gives the immediate cosmetic result, while the leave-on product helps address buildup over time. But no single product makes blackheads disappear permanently for everyone; genetics, hormones and environment all influence how visible they are.
If your blackheads are very persistent, widespread, or painful, it is reasonable to ask a dermatologist for individual advice; that goes beyond what a cosmetic nose strip can address.