If you see a blank red box above, Flash Player is not installed or enabled.
Install it from here.
If you see a Flash Player information icon, your Flash Player is timebombed.
Patch your Flash Player using this tool.
If you see your Flash Player version, you're good to go!
Note that most modern browsers don't support Flash Player anymore.
Compatible browsers for Windows include Microsoft Edge's Internet Explorer Mode, Waterfox Classic, K-Meleon, Pale Moon, and Basilisk.
Waterfox Classic is recommended for Mac users. Pale Moon is recommended for Linux users.