If the clipboard never works, you might be infected with malware. If the clipboard never works, even with Firefox closed, it is not a Firefox problem. Firefox does not allow and even prevents your computer from getting malware. If the clipboard never works only when Firefox is open, proceed to the next section.
Malware (malicious software) can prevent the clipboard from working. Some malware that causes the clipboard to never work are:
Some Rich-Text Editors have copy and paste buttons that override this feature. This is because of security reasons, Mozilla does not want any sensitive information being pasted and than submitted without your permission.