I am having the same problems. I have a 1Password3 Family license, i just did a clean install of my mac and i could not install the proper safari extension.
It shows me the Message: https://i.imgur.com/XhlPe0z.jpg
But even after clicking the trust button, nothing really happens. What could i do in order to get the extension going?
I'm sorry you're having trouble installing the extension in Safari! Since you're using 1Password 3, I've moved your message to our "1Password 3 for Mac" forum. I hope you don't mind!
First, please make sure you're installing the correct extension for 1Password 3. From the main 1Password 3 app, go to the menu for 1Password > Install Browser Extensions, and that should take you to the following site for the 1Password 3 extension: https://agilebits.com/extensions/mac/index.html
On that site, click the 'Download' link next to Safari. Does that help to install the extension or do you have the same problem where you click the 'Trust' button but nothing happens?