PROBLEM
References can't be transferred to RefWorks, because the browser in use has disabled popups.
Solution:
If the browser has disabled popup windows, references can't be transferred to RefWorks.
If you can't allow all popups for security reasons, you can manually select to allow them just from a certain database. When you transfer a reference from a database for the first time, your browser should ask for a permission to allow popups for just the page you're on at the moment.
Instructions for different browsers are shown below.
PROBLEM
RefWorks tab doesn't show in Word
Solution:
Activate Write-N-Cite in Word with the guide showing below. Word should be restarted for the changes to apply and RefWorks -tab to appear.