Some info from @ludmila over in the Hyundai thread. It's the same company runnig the promo, so all the info should be relevant to Suabaru as well.
If the above doesn't work, try this.
Nothing helped for the GC not received, dealer stopped responding, urban science responded by email that they contacted dealer and dealer will respond, did not work. So I went back to dealer, and said this is false advertising, I had all the paperwork , and the dealership manager said it was past the date that he can enter the code, so he gave me a check for $50.