Attempts at having an Article V convention have been stunted by the true need for action. COS is partisan in nature and because of this cannot represent a large majority of the country. The measure was could have been but was not taken up by the US Congress. USTL has a moderate proposal but has shades of partisanship, perhaps from both parties. Its potential positive effect is not easy to grasp. WolfPac is promoting and idea that, by choice, was not taken up by the US Congress. COS and WolfPac are promoting ideas that may be addressed more easily by legislative action that by amending the Constitution. These weaknesses have resulted in temporary failure of these measures.
21st Century Democracy does not have a partisan leaning. There is zero motivation for Congress to address this because it negatively affects congressional power. The measure also creates a degree of oversight of the US Supreme Court.
Lack of a previous Article V convention is understandable because the need did not exist. Most measures started as applications to an Article V convention ended up being addressed by Congress. And oversight of the Supreme Court was not seen as a priority until now when the likelihood of a biased Supreme Court has increased substantially.