I assume you downloaded the two expansions with impulse?

When on the My Games tab are all three present?

When you right click on SoaSE and select view registration, does the pop up window show your serial number?

With Impulse running, click the blue box in the top left corner and in the drop down box, select register a product.  If Sins is not present try to add a registration putting in all of the information you used when you first registered.

When all else fails, contact [email protected] and explain to them your situation, include your serial number and preferably, send the email from the account you used to first register the game.  Once they verify everything, they can sort you out and get things working for you.