It is possible (although not common) for a new law to be enacted that affects a case that was previously filed.
If that has happened with your case, resulting in a Motion for Summary Judgment being entered against you, then your attorney should at least be willing to discuss with you what happened. (They may not be able to change the circumstances or the law - your attorney is not responsible for what the legislature or the courts do in this regard - but they are responsible for communicating with their client).
If your attorney believes that an appeal is appropriate, then they should explain to you why they think that appeal has merit in the face of the law that the trial judge found against you on the MSJ.
A "dismissal with prejudice" does mean that you cannot file the case a second time. (This can be compared to a "dismissal without prejudice" which allows you to file again).
(If your attorney continues to refuse to communicate with you, follow up with a letter, ask for them to respond. If they fail to respond, write again, but this time cite the Tennessee Rules of Professional Conduct and the Attorney's Obligation to Communicate, and refer to your earlier letter and phone calls. If the attorney still refuses to respond, then you can consider filing a complaint with the TN bar association, and possibly bringing a malpractice action (although again, this is going to be limited to pursuing them for their failure to communicate and negligence, it may not cover the loss of your case - if this was due to the change in the law, this is beyond the scope of influence of your attorney and a malpractice claim would not reach that).