According to this story, the Wisconsin Libertarian Party has asked the state to suspend petitioning for the general election, or to deem any parties that were ballot-qualified in 2018 to also be ballot-qualified for 2020 as well.
Currently, the only parties that are ballot-qualified in Wisconsin are Democratic, Republican, and Constitution. The Libertarian and Green Parties went off the ballot in November 2018 because they had no nominees for statewide office who polled as much as 1% of the vote. Both parties had gubernatorial nominees, but no nominees for any other statewide office. The gubernatorial election of 2018 was extremely hotly-contested between the two major parties, and the vote was very close, and in conditions like that, the minor party vote is generally smaller than normal.
The Constitution Party survived 2018 because it ran for Attorney General and Treasurer, and received over 1% for both.