I've been using Opera and 1Password4 for a year without a hitch. Now suddenly just two days ago I got this problem too. The 1Password plugin does (close to) nothing. I cannot make it open the "Unlock 1Password Vault" window, or anything else.
I have reinstalled the plugin and even the software.
One thing I've noted is this: If I select "Restert 1Password Helper" from the client, and then click on the Plugin, it will open a new tab and do its "Looking for the 1Password helper" for a while, before telling me "Couldn’t connect to 1Password "Either the helper is not running, or something is preventing it from communicating with the 1Password browser extension".
I can do this all day. If I relaunch the browser it again will seemingly do nothing until I restart the helper, in which case I'm back to the error above.
Also pingback to this this
On the same system everything is working fine for Chrome.
Opera 42.0.2393.85 Stable
Windows 64bit 10.0.14393
Works fine on my Win7 machine, all same other versions (same vault).
1Password Version: 126.96.36.1996
Extension Version: 188.8.131.52
OS Version: Windows 10 x64
Sync Type: none/local