I installed the latest UiPath 19.5.0. Whenever I try to open an exiting or new project in it, it gets stuck at the Opening message screen as shown in figure below.
You can also try to remove .json (backup it somewhere). And open project from Main.xaml. Then you need to download any packages/dependencies which were used in project and new json file will be created. It can be than you json file have a issue if was created in older version of Studio.
Sometimes when trying to open old project in new version of Studio json can’t be properly read. Like it’s protected or something. This is happening from time to time especially when old projects were made in very old Studio. Sometimes the version of dependencies used in old project are also so old that newer Studio can’t get them. Sometimes OS by itself is not correctly saving files. I think in your case it was just bad luck