The strange thing is that it worked normally in macOS 10.15.3 before I updatd the system. Then I try to reinstall R2019b(PS: I changed the default installation path to "/Applications/Matlab_R2019b.app" for launch convenience) and it runs without any problem at the first opening after reinstallation. But it becomes no responding just when I open it at the second time.
I find that if I change the matlab directory name in folder /''Applications'' (for example Matlab_R2019b.app to MATLAB_R2019b,app) it can start and run normally at the first opening after renaming. But it gets stuck again from the second opening.
I also confirm the stuck problem. It seems the stuck occurs very frequently on macOS10.15.4 with MATLAB 2020a and also 2019b. The freeze usually lasts seconds to even a minute. Then it comes to normal.
There is an issue with the way Accessibility features work on macOS with MATLAB at this time.
You can follow these steps:
Go to System Preferences > Security & Privacy > Privacy > Accessibility. This list shows all the applications that you've given permission to use the Accessibility API. One of these applications is triggering the bug in MATLAB and causing it to hang.
You'll need to use a process of elimination to determine which application is preventing MATLAB from starting. It is likely to be an app that gets and sets information about other application windows.
You can also select a web site from the following list:
How to Get Best Site Performance
Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.