Facing Yahoo Mail login problem can occur due to various reasons. Firstly, incorrect login credentials such as username or password can lead to access issues. Secondly, security measures like two-step verification might cause login failures if not properly set up. Additionally, browser-related problems, like outdated cache or cookies, can hinder login attempts. Network connectivity problems or Yahoo Mail server issues could also be culprits. Account security concerns, like suspicious activities or hacking attempts, might result in login difficulties.