There are 2 new security features.
1. A user has to click inside the autofill fields, the arrow (interaction) for the autofill to work.
2. If the site is not a secure one, the URL text will turn red in the search box..
Quoting from the below linked HowTo article:
Safari Login AutoFill
Available for: iPhone 5s and later, iPad Air and later, and iPod touch 6th generation
Impact: A malicious website may be able to exfiltrate autofilled data in Safari without explicit user interaction.
Description: Safari autofill did not require explicit user interaction before taking place. The issue was addressed through improved autofill heuristics.
At present this may not work consistently across all sites that require login.
From my experience, a combination of tapping the AutoFill fields, tapping the arrow button, entering the
info manually and tapping the "enter" key helps.
I am posting this as a user like you.
Note: This doesn't represent Apple's view on this, just my own view.
To send a Feedback to Apple: https://www.apple.com/feedback/safari.html