If you navigate to your 'Payments' tab in OGAds (see below), but don't see any invoices, it is most likely due to the timing of your earnings.

Invoices are created by Tuesday morning (sometimes earlier) each week for the prior week's earnings.  For example, any money earned from 12/05/2016 through 12/11/2016 will be posted to your account as an invoice by the morning of 12/13/2016.

The second reason an invoice wouldn't appear in your account is if you have not yet reached $50 in total earnings.  No invoices will be created until that milestone has been reached.