The bug you referenced in Comment #7 explains what is happening.
The UserCorner sets a cookie with an invalid name, and other applications on the same domain fail to parse the HTTP request.
So reinstall does not help. Clearing browser cookies, or better, deleting a cookie from your server's domain, should solve the issue. You can try another browser or an incognito window, do not go to UserCorner, but straight to SchoolTool.
There is a workaround in that bug, you need to modify one system file.
The bug you referenced in Comment #7 explains what is happening.
The UserCorner sets a cookie with an invalid name, and other applications on the same domain fail to parse the HTTP request.
So reinstall does not help. Clearing browser cookies, or better, deleting a cookie from your server's domain, should solve the issue. You can try another browser or an incognito window, do not go to UserCorner, but straight to SchoolTool.
There is a workaround in that bug, you need to modify one system file.