Abbey, first of all, please specify what payment provider you are using and make sure the IPN is configured correctly (read this thread for more information: http://www.oxwall.org/forum/topic/14960)
Then, please check the status of the payment on your PayPal account (or any gateway you are using) - the payment status should be active.
Please go to phpMyAdmin > ow_base_log table, search for the latest entry and check whether there is any error message related to this payment.
Finally, check whether the payment was added into the Finance section (Admin Area > Dashboard > Finance).
You can collect all this information and send it to us.
If the payment did not appear in the Finance section, that means that the payment hasn't been completed. Did you checked the payment status? Did you checked the ow_base_log table.
Abbey, we want to assist you with this issue resolving, but the information you have provided is not enough. The more details of the problem you provide - the more effective our help will be.
Dear Abbey,
As far as I can see you are using your Merchant ID, but not the PayPal email - this is the probable reason of the issue you've got faced with. Please add your PayPal email address instead of Merchant ID and try to purchase the credit pack once again.
Once the payment to be completed, make sure that the entry about the payment has appeared in the Finance section.
The plugin was developed at that time when the PayPal email meant the Merchant ID. But, later they separated these two entities. Our plugin does not work with the Merchant ID and due to this, we are facing a lot of problems related to the misunderstanding. So, we are going to rename the configuration or make PayPal plugin work with both Merchant ID and PayPal email.
Abbey, does your post mean that the problem is solved?