Enable Accessibility Access for PopClip
For PopClip to work, it needs Accessibility API access. You can turn this on in System Preferences, as follows.
1. Go to System Preferences and open the Security and Privacy pane.
Select the Privacy tab.
Click the Accessibility category.
If necessary, click the lock and enter your password.
Enable PopClip by checking the box.
If PopClip is already shown as enabled, uncheck and check it again.
If PopClip does not appear in the list, restart your Mac. It should then appear in the list.
Why is this necessary?
PopClip uses an OS X feature called the Accessibility API to read the text you select in other apps. This lets it do things for you, like check the spelling or look up the words in the dictionary (and all the other extensions).
The user must approve each app's access to Accessibility features, so this step is needed before you can use PopClip.
PopClip only uses the Accessibility API to read the text you select with your mouse. No information is stored or transmitted anywhere.