1Password 3 was created in 2009 and has not been under active development since 2012. It supports OS X Snow Leopard and Lion, so is not compatible with recent operating system (OS) and web browser releases and won't be receiving updates in the future. Since we use 1Password to help us be more secure, it's important to stay up to date with not only 1Password, but also OS and browser updates, which contain important security fixes.
If you've purchased 1Password for Mac version 3, you're entitled to use it on all of your compatible devices indefinitely. It never expires, but is only valid for the version you purchased. If you'd like to always have the newest version, along with many other benefits, you can sign up for a 1Password.com membership. This works with macOS Yosemite, El Capitan, Sierra, and High Sierra, and supports the latest versions of major browsers.
If you're unable to upgrade, you can still use 1Password 3 in a limited fashion, bearing in mind the security risks, and that you may encounter some compatibility issues introduced in recent years:
The import feature (File > Import…) in 1Password 3 relies on system libraries that were updated in Mavericks, so the import feature in 1Password 3 does not function in Mavericks or later. The only workaround is to use 1Password 4 or later to import.
1Password 3 may not correctly identify that the Dropbox service is running. If this is the case the Move to Dropbox… button in the General tab of 1Password 3 preferences will not work. If this happens to you the workaround is to right click where it says
1Password.agilekeychain and select the third menu option in the context menu that pops up (Move Data File To Another Folder…). You can then select your Dropbox folder.
Recent macOS releases render text fields invisible when editing an item. The text is still present, it just can't be seen (as in these image examples: edit title, edit username). You can safely make the changes you wish, and they will be visible once you save.
1Password 3 does not work on macOS Mojave. You'll need to upgrade to 1Password 7, which is included with a 1Password.com membership. It can import data from an AgileKeychain vault using File > Import > 1Password Keychain.
If you purchased a license from the AgileBits Store, you'll need to download the 1Password 3 app.
If you purchased through the Mac App Store, you'll need to install it from the "Purchased" tab in the App Store on your Mac with the Apple ID used for the purchase.