fixed with recent update

Version: 38.0.2220.41 - Opera is up to date
Update stream: Stable
System: Mac OS X 10.11.5 64-bit

When I enter credentials and click sign in, nothing happens. No redirect, no failures, nothing. The logon page opens in a pop-up and none of the buttons work. If I hover over the link address is displayed at the bottom of the window. Works fine with Safari

I'm not familiar with Last Pass but I had the same issue with Enpass. I deselected Verify Bowsers and then Enpass works.