Note: This problem is not the same as Flash Player crashes or freezes in IE9 or poor sound/picture quality (although some of the repair steps may also help in those situations) – see ‘Flash crashes in all web browsers‘.
Problems with Flash videos in IE9 have a number of possible causes so there are several possible fixes – work through them in order, restarting IE9 and retesting videos after each step to see if the problem is fixed:
1. Disable ActiveX filtering – ActiveX Filtering in IE9 lets you browse the internet without ActiveX controls. However, Flash Player is an ActiveX control so, if this feature is enabled, you won’t be able to play Flash videos.
Open IE9 and click on the gear/cog icon in the top right corner. Click ‘Safety’ then uncheck (untick) the ‘ActiveX Filtering’ menu item if it is ticked.
2. Enable Flash Player plugin – Browse to Adobe’s ‘About Flash Player’ page then click on the IE9 gear/cog icon in the top right corner. Click ‘Manage add-ons’ to open the Manage Add-ons window. Click the ‘Toolbars and Extensions’ tab in the left hand panel then find the ‘Shockwave Flash Object’ entry in the right hand panel.
Look at the ‘Status’ of this entry – if it is ‘Disabled’ then select that row and click the ‘Enable’ button at the bottom right of the Add-ons window to enable it. Click the ‘Close’ button to close the Manage Add-ons window.
3. Disable GPU (Hardware) Rendering – Hardware acceleration is a feature in IE9 to move graphics rendering from the processor (CPU) to the Graphics Processing Unit (GPU). In some cases (especially older computers) this may cause problems viewing Flash content.
Click on the IE9 gear/cog icon in the top right corner then click ‘Internet Options’ to open the Internet Properties window. Click the Advanced tab and, at the top of the Settings, select (tick) the ‘Use software rendering instead of GPU rendering checkbox.
Click Apply and OK then restart IE9 to test.
4. Reinstall Flash Player – Download the Flash Player uninstaller from Adobe here and follow their specific instructions to completely uninstall Flash Player then restart your computer. Now open IE and install the latest version of Flash Player from Adobe here.
5. Restore IE9 Advanced Settings – Having reached this point, if the videos still do not play then it is very likely that IE9 itself is to blame, not Flash Player. This step resets IE’s advanced settings to their defaults (as they were when you first installed IE).
Click on the IE9 gear/cog icon in the top right corner then click ‘Internet Options’ to open the Internet Properties window. Click the Advanced tab then press the ‘Restore advanced settings’ button. Click Apply and OK then restart IE9 to test.
6. Reset IE Settings – This step restores IE to the condition it was in when you first installed it – it resets far more than the previous step (including most user settings but not your favorites or feeds). Click on the IE9 gear/cog icon in the top right corner then click ‘Internet Options’ to open the Internet Properties window.
Click the Advanced tab then press the ‘Reset’ button. The ‘Reset IE Settings’ confirmation window opens – don’t tick the ‘Delete personal settings’ box unless you don’t mind losing the settings specified (especially saved passwords).
Click ‘Reset’ then the ‘Close’ button when complete and ‘OK’ to confirm then restart IE to test – you will need to set up IE9 again as if it had just been installed.
7. Reinstall IE9 – If Flash videos still do not play it appears that IE9 is too corrupted for the previous resets to fix. If you uninstall IE9 completely, the previous browser (IE8) will then become operational again. A guide to uninstalling (and reinstalling) IE9 is available from Microsoft here.
After uninstalling, test that the videos now work in IE8. If they don’t (and you followed all the previous steps) then your problem is a very unusual one – you may need to use a different browser (e.g. Firefox or Chrome) or investigate further with Adobe and/or Microsoft – or (worst case) try a repair/reinstall of Windows…
If videos do play in IE8 then you can safely reinstall the latest version of IE9 – a guide to installing IE9 is available in Microsoft’s guide above.
In my case the first 6 steps did not work because the problem was caused by IE9 corruption (step 7 worked fine) but there are several causes of Flash videos not playing in IE9 – you may not need to complete all of these steps to fix it.