1. Your visa is an e-visa, and the information is stored in official website or mobile phone application, not posted on your passport. In this case, you need to use the official website or mobile phone application to verify whether your e-visa has been successfully approved.
2. There may be something wrong with the visa information posted on the passport, which leads to the information not being displayed clearly. For specific reasons, you can contact the Korean embassy or consulate to help solve it.
3. If there are some problems in the process of visa application, the visa may not be displayed normally on the passport. In this case, you can consider re-applying for a visa and ensure that accurate information and materials are provided during the processing.
If you have any questions about the specific situation, I suggest you contact the Korean embassy or consulate for consultation.