Hi weisinweisin,
Thanks for the update. Given this is also happening when trying to login to ASC with your Apple ID, I'm wondering if you have a content blocker enabled in Safari that's preventing any type of logging in. Go to Settings > Safari > Content Blockers, disable anything listed, and then try logging in again.
With iOS 9, Safari brings Content Blockers. Content Blockers are extensions that let Safari efficiently block cookies, images, resources, pop-ups, and other content.
To turn on Content Blockers, you need to download a content blocking app from the App Store. Tap Settings > Safari > Content Blockers and enable the extensions that you’d like to use. You can use more than one content blocker.
Safari web settings on your iPhone, iPad, and iPod touch
Also make sure you're not completely blocking cookies:
To set whether Safari blocks cookies in iOS 8 or later, tap Settings > Safari > Block Cookies and choose one of the following: Always Block, Allow from Current Websites Only, Allow from Websites I Visit, or Always Allow. In iOS 7 or earlier, choose Never, From third parties and advertisers, or Always.
Some pages might not work unless you accept cookies. For instance:
You're unable to log in to a website or webpage using your correct username and password.
Have a good one.