I too am having problem with 1Password and the Safari Extension on my Mac syncing and, essentially, working on Safari. I have noticed a couple of things that may help in diagnosing and resolving the problem. Whenever i clear ALL the history from (cache and cookies) from Safari (which I do frequently... daily+) that seems to be when the 1PW extension will not work. When I click on the 1PW icon in my Safari toolbar I get the large pop-up box saying 'Open 1Password', but either it shows 'syncing' and/or simply won't open 1Password. The way to fix it is to a) delete all history, b) untick the Safari extension in Safari Preferences, c) shutdown Safari, d) restart Safari and tick the 1Password extension in Preferences. This brings up a window showing, essentially, a install or activation of 1Password and I click on "I'm all set". `After that 1Password works... unless and until I clear all my history again!
Hope that helps. I'd like to hear when a fix or workaround has been identified.
Cheers, Erik