The treaty has inherent flaws, another treaty or amendments are necessary to achieve a real ban
The main problem with nuclear weapons treaties is that they are ambiguous, despite claims to the contrary, neither the NPT or the newer Nuclear Ban Treaty functions as a comprehensive nuclear weapons convention. As a result the legality of Nuclear weapons remains elusive and the problem remains unsolved. The lack of voting UN members is another issue, if all nuclear powers and NATO abstain from voting, it is likely that some may also challenge an effective ban treaty outright.
Countries like Israel are widely considered to posses a large number of nuclear weapons but remains aloof on the subject, not affirming or denying their possession and not voting on treaties regarding nuclear weapons. This puts the usefulness of this treaty in question as the treaty, through encouraging self disarmament, may increase the likelihood of nations cheating in regard to international commitments. The Treat on the Prohibition of Nuclear Weapons may successfully stigmatise states with nuclear weapons, but it will take great strides in diplomacy and defence to develop an effective treaty that prohibits these weapons entirely.