If QQ International doesn’t let you add any more contacts then you have probably sent out too many friendship requests in a short amount of time. In this case our system will first give you a warning, and then will temporarily disable your account for up to 24 hours if you keep sending contact requests too frequently.
More particularly, if you receive an error message saying that your account has been locked for “over-frequent operation or suspicious behavior” it indicates that someone has reported you for inappropriate activities such as posting advertising information when adding new contacts.
We do not tolerate spamming or unsolicited advertising – please refer to our Terms of Service and thank you in advance for your understanding.
Another reason for not being able to add new contacts to your QQ International friends list is that you have probably exceeded the limit of 500 contacts for regular QQ accounts (1000 if you have a VIP account).