What could prevent a business practitioner from sending an email proof of a journey?

The ability to send an email proof of a journey is contingent upon the successful setup of test profiles within the Adobe Journey Optimizer framework. A test profile is essentially a mock user account that allows practitioners to see how communications, such as emails, will appear to end-users without actually sending them to a live audience. If a test profile has not been created with the specific email address intended for the proof, the system will not have access to the necessary recipient information to generate and display the proof correctly.

Additionally, while factors such as server status, journey publication, and network issues can impact the overall functionality of sending emails, they do not specifically relate to the prerequisite for ensuring a test profile is in place for proofing journeys. Thus, without the appropriate test profile, the system cannot simulate the journey proof, making this the correct answer.