About the issue
In September 2019, Apple discontinued the Safari Extensions Gallery, which was required to install the 1Password 6 extension in Safari.
From now on, Safari will only support Safari App Extensions like the one included in 1Password 7. Because of this change, you can no longer install the 1Password 6 extension in Safari.
The last update to 1Password 6 for Mac was in May of 2018. It will only receive critical security updates in the future.
What you can do
To use 1Password in Safari, you’ll need to upgrade to 1Password 7 for Mac.
If you don’t want to upgrade to 1Password 7 right now, you can still use 1Password in other browsers, like Chrome, Firefox, Opera, or Vivaldi.
Get more help
If you don’t know which version of 1Password you’re using, open 1Password. From the menu bar, choose 1Password > About 1Password. Get help if 1Password 7 isn’t working in Safari.