See if the browser you are using is IE browser. If multiple browsers are loaded at the same time, I have to uninstall the other browsers. I had a similar problem at first, because I used to use TT browser, but I uninstalled it later.

In addition, if you are going in for the first time, you should download a jre software. The method is as follows: After entering the online training platform, click "Online Classroom" and there will be a "Enter the classroom, learn progress" in the middle of the interface. Click "Enter" below, and an interface will pop up. Click "Download Components" after the red word. After downloading, exit the website and re-enter the class (remember: download)