Why MATLAB 2019a delete itself after installation?

I download MATLAB 2019 from this website. In the installation process, I changed the directory to D drive and then installed it. When I finished, I open the root directory and found the matlab files are disappearing (it deletes itself!!!!) After one minute, all gone. I remember the last step in the installation is "activation", but when I click next, nothing appears, the program exits so I thought it is finished. Can anybody help with this problem I really appreciate, I've been installing matlab for two days.

[Star Strider]

Click on the Contact Us link (the telephone handset icon in the upper right corner of this page) to ask MathWorks. Click on Contact Support, then Installation Help.

[ZHU Chen]

Thank you!

[Star Strider]

My pleasure!