The way you have explained it is perfect. Not too informal, just right. While your expalnation paragraph is perfect, the title sentence would sound better like this: "I am unable to enroll in this training program". Or: "I can't enroll in this training program".

Original: "I can't get enrolled in this training program." (We would not say this.) Your meaning is unclear. WHY can't you enroll in the training program--no money, encountering an online application error? If no money: I can't enroll in this training program because I can't afford it. If processing error: I am unable to enroll in this training program because the online enrollment process keeps giving me an error and won't let me continue.