Muse app is discontinued and unsupported now. The only way to get Muse is through a paid subscription to the Creative Cloud ALL APPS plan. And check the option to Show Older Apps from your Creative Cloud desktop. Use Muse at your own risk. Eventually, all Muse sites will start to fail, some worse than others.
================ Important Announcement about Muse As of July 31, 2020 sites published using Adobe Muse will no longer be editable with Adobe In-Browser editing solution.