When the flash player stops loading from one day to the next, it's
possible that a recent DLL update to
C:\Users\\AppData\Local\Google\Chrome\User
Data\PepperFlash\20.0.0.xxx\pepflashplayer.dll is the cause. The xxx
can vary over time: 267, 286..
To test the DLL, hide/rename it as pepflashplayerHide.dll. Close/open
Chrome, which will now use it's builtin DLL. If the player works,
you've found the culprit. You can stop with the Hide workaround or try
to fix the problem.
To correct the problem, delete the PepperFlash folder. Close, open
Chrome: the flash player should load. If the problem reappears (after
the folder auto updates), there may be permissions problem (see
below).
--Details-- The DLL won't load if it's 32/64 bit-type doesn't match the bit-type of Chrome. A mismatch can occur when you switch 32/64-bit
Chrome versions and there was a flash player security update lately
(here 12/24/15).
Type about:version in the address box to see the Chrome bit-type.
To check the type of the DLL update, look at it's size. (See the
PepperFlash path above) Sizes under 17000KB are 32-bit, over 28000KB
are 64-bit.
If the bit-types don't match, delete the 20.0.0.xxx folder. If the
bit-types match, there can still be a permissions problem - delete the
PepperFlash folder.
When you hide the DLL or delete the folder, Chrome will fall back to
it's builtin version and flash should work.
After deleting the folder, you'll get an auto-update soon (usually <30
min). Or you can update it immediately from about:components.
If the problem returns with the update (watch the PepperFlash folder),
try running Chrome as Administrator. If this lets the plugin load,
there may be permission problems.
You can circumvent the permissions failure by hiding the DLL again,
see above. This will block additional updates (to this 20.0.0.xxx) and
use the less secure builtin DLL. Quick, but not optimal.
The better approach is to fix the folder permissions.. You only need
to fix the 20.0.0.xxx folder, the critical permission is 'Read and
Execute'. Try this succinct Best Answer (old but good) or see
this recent longer one.
The 32/64-bit conflict is being worked as bug 546017.
Institutional users may see the same "Couldn't load plugin" failure,
but this is related to network share permissions. See bug 572131
for details.