Since version 3.4.0, Papers 3 for Mac has required a Macintosh computer running OS X 10.9 Mavericks to OS X 10.15 Catalina. Papers 3 support ended on Dec 31, 2020, and is no longer tested on newer OS (Big Sur). To continue using Papers 3, please do not upgrade to the newer OS. We encourage users looking to run the latest OS, to please consider upgrading to the latest version of Papers (released Nov 2018).