Like most of the cases for the can’t sign into Yahoo account issue on other devices, if you can't check in to Yahoo Mail on iPad, the possible reasons might be as follows:
1. Using incorrect username and password
2. Yahoo Mail server is down
3. Slow or poor internet connectivity
4. Outdated OS
If the above-mentioned pointers are ensured; however, you're still facing issues while signing in to your Yahoo account, restart your iPad to resolve the difficulty can’t sign into on iPad. to try to to this, press and hold the facility button and one among the quantity buttons together. once you notice the facility off slider, drag-down the on-screen slider and wait until the iPad shuts down completely. Lastly, press and hold the facility button until the Apple logo appears on the screen.