This makes it work for me in MPC-HC:
C:\Windows\SysWOW64\Macromed\Flash\mms.cfg
Code:
AutoUpdateDisable=1
EOLUninstallDisable=1
SilentAutoUpdateEnable=0
DisableDeviceFontEnumeration=1
AllowListPreview=1
TraceOutputEcho=1
EnableAllowList=1
EnableInsecureAllowListLocalPathMatching=1
AllowListRootMovieOnly=1
AllowListUrlPattern=file:*
Note: Requires Windows 7 and Flash 32.0.0.465. It does not work on Windows 10 which uses Flash 32.0.0.445 (this version seems to be buggy as it also failed on Win7).
Alternatively you can use
RunAsDate tool on MPC-HC to fool the Flash plugin with a fake date.