There are two reasons that your distributor might not be listed. Firstly, you should check that they haven't been inadvertently filtered out. You can check this in the corporate settings for the Public Price Suppliers. If you don't have access to this section, please contact your Corporate administrator.
Secondly, the distributor might not be listed in the details pane for the part. For example, in the Amphenol part below is also distributed by Digi-key. BOM Advantage automatically chooses the distributor for the part based on the best price and the best price confidence (that is, how likely it is you will be able to execute on the price).
If you wish to see all pricing that BOM Advantage has gathered, click on the part link and select the Pricing tab.