Make sure that your Payout is set on the Settings sections of the sites/profiles you're trying to promote. If it is already set then try increase the Payout. The higher the payout the more exposure you will receive. If you're still not receiving enough exposure at the highest setting then you can get Premium to increase your Payout further.
Another reason your Points may not be used is if your account has become "Inactive" for more than 7 days. To resolve this simply log back in to make the account "Active" again!