I also use the Yahoo Mail app for Android, and to my surprise today (February 27th, 2024) I couldn't open my email account using the app. Occasionally, Yahoo will have trouble opening up, but I do not recall it having issues for such a long time as they've had today - Yahoo Mail app is still down at the time of writing this, both for Android and iOS. I did check to see if it's a worldwide issue and that's the case, as they've posted a message on the official Yahoo Twitter account that the apps have issues and that those will be solved soon, as their technical team is currently investigating the cause.