I used this Account login page at Tunnel Bear, my VPN, (https://tunnelbear.com/bear/account#/login) and it always shows my useID/password as incorrect when I use the Extension to autofill the login. For the past few days, I've been working with Tunnel Bear to see if there is an issue.
Long story short, we've found it's not them. When I use this older Account login page (https://www.tunnelbear.com/account/login.html) the Extension works fine.
I've even reset the URL in the main 1Password App, as well as all my account info, and it didn't make a difference. Only this URL causes an issue, the other URL work fine.
I can still see my Account page, so it's okay for me, but I thought I'd put it on your radar incase it might relate to other issues.
1Password Version: 6.1
Extension Version: 4.5.3
OS Version: 10.11.3
Sync Type: iCloud