Blank space or “Adobe Flash Player required” message showing instead of player
If these messages are being displayed instead of the player, it is very likely that your theme doesn’t call the wp_footer() function in the footer or the wp_head() function in the header. These function calls are very important because without them, plugin developers cannot insert code into the header and footer sections of the page.
To fix this, open the footer.php file of your theme and add this line just before the closing <body> tag (if it is missing).
<?php wp_footer(); ?> </body>
And open header.php file of your theme and add this line just before the closing <head> tag (if it is missing).
<?php wp_head(); ?> </head>
Player not showing in Firefox 3
- Do you have the Adblock extension installed? In Firefox 3 Adblock incorrectly blocks Flash content, even if your entire page is whitelisted. In this case just disable Flash block. Or use Adblock Plus instead.
- Just make sure that you have the required minimum version of the Flash Player installed.
- Ensure that you don’t have a corrupt Flash Player by uninstalling the Flash Player using the Adobe uninstaller and by reinstalling the plug-in via the Adobe Flash Player installation page.
Taken from the swfobject FAQ page.