Why don’t services appear in the purchase transaction I created from the contract?

Because the purchase transactions you create from the Work Items tab in the contract copy materials only. If you select work items that contain materials and services, the materials are copied to the form and the services aren’t.

If all the items you select are services, the Purchase Options button doesn’t appear in the bar at the bottom of the screen.

Solution: if you need to purchase a service, add it manually using the Add button in the purchase transaction form before saving.