The message 'Plugged In, Not Charging' on your HP laptop may indicate several potential issues. It could be due to a faulty or aging battery that no longer holds a charge effectively. Additionally, a damaged charging cable or port may disrupt the charging process. Outdated or corrupted battery drivers might also lead to this message. Some laptops have power management settings that limit charging to prolong battery lifespan. Finally, software conflicts or glitches could be a factor.