You may find that you cannot play the flash in your pdf file, actually Adobe has ended support for Flash Player at the end of 2020, so Adobe Flash Player versions newer than 32.0.0.344 would refuse to run any custom flash content , instead it would just show this icon as the below screenshot.
For more information, see Flash Player end-of-life.
If you want to play the existing flash, you may try to install the earlier version, such as 32.0.0.255.
And the content creators will be recommended moving away from using Flash content (*.flv and *.swf) in all multimedia workflows in PDF and migrate any existing Flash content to new open formats, such as HTML5, WebGL, and WebAssembly.
