" LinkedIn has policies in place to stop behavior that other people may find abusive. Unfortunately, we’ve determined that you used a feature in that way, even if you didn't mean to.
We can often lift a restriction after you acknowledge you've read some educational information on proper use of our site.
The most common reason for a restriction is sending too many invitations to people you don't know.
A restriction is automatically triggered if too many invitations are:
Declined by the recipient with the I don't know response. Flagged as spam.
Tips to prevent restrictions:
Invite only people that you personally know and who know you. Invite only those you'd recommend to others. Personalize your invitation message. Explain how you know them or why you want to connect. Add a current picture of yourself to your profile so people recognize you. Use an InMail or Introduction if you don't know someone's email address. Use the Ignore button for invitations from someone you know but choose not to connect with. Only use the I Don't Know option when you truly don't know the member."