I will talk with you about "legalities" and "realities" from 21 years split between being a judge, a prosecutor, and a criminal defense attorney. Legalities- The DA does need to prove the jury that your boyfriend knew about the existence of the restraining order by being served with a copy of it. Whether they try to prove that through the previous RO or the current one, we do not know. However, if the prior case was dismissed, that RO is out and they would need to prove the current RO. If you were served with a subpoena through personal service, you are court ordered to appear at trial.
Realities - it is hard to prove any domestic violence case with an uncooperative "victim" or witnesses. So, he does have a "fighting chance." Additionally, your boyfriend will have a much chance of beating the charges with the assistance of an attorney. So, I hope that he either has a court-appointed attorney or has hired an attorney.
The information provided in this answer does not create an attorney-client relationship. If you are interested in his legal services, feel free to call Chris at (303) 409-7635 at his law office in the Denver Tech Center. All initial consultations are free of charge.
If your boyfriend was never served a copy of the new protection order, there may be a defense that he did not knowingly violate the order. It is typical that at first advisement in Weld County that the defendant is given a copy of the protection order and signs that order in front of the court. Sometimes that does not happen until a later appearance due to it being overlooked. Until a person is on notice of the order, it is difficult to show that a person violated that order.
If you have been served with a subpoena, that is a court order requiring you to appear at trial. There really isn't enough information here to answer your question about whether or not the DA could go forward without your testimony. That would depend on a number of factors, including whether or not there are other witnesses who can testify to the facts of the violation.