Check that PDF receipts are active in your Sphere account and that PDF receipts were generated for the gifts you're examining.

To check that PDF receipts are activated for your Sphere account:
  1. Go to Control > Administration > Organization Setup > View/Edit Org Info. 
  2. Scroll down to the PDF Receipts section.  You should find that Enable PDF Receipts for Account is set to Yes.
To determine if a PDF receipt was generated for a payment:
  1. Go to the location for the event in which the payment was made (often this would be Communities > Special Events > Friends Asking Friends > Kintera Thon).
  2. Click on the name of the event.
  3. Click on View Reports.
  4. From the Run Quick Reports dropdown, select PDF Receipts.
  5. If seeking a particular record, you can utilize the Transaction Date Range and Customize Report features to narrow the results.
  6. Click Finish.
  7. Select No - Run report immediately so you can view the results.  Verify that a receipt number exists for the gifts in question.
If you find both of these are the case and their matching Raiser's Edge record has no value for SphereReceiptNumber please Contact Support and reference this article. 

Any screenshots you can provide will be helpful.