I'm in the Army and a soldier in my platoon performed 45 days of extra duty months ago and has yet to actually receive an article 15. What are the consequences and options for the soldier?

For an answer to this you really need to contact your base or post Legal Affairs Office. They would be in the best position to determine if the proper discipline was applied to your soldier. Consider this: Maybe he volunteered to perform the 45 days of extra duty to PREVENT himself from receiving the Article 15. (??)