There's a known issue in Policy Server 12.52SP1CR02 for which this parameter has out of the box typo. The default ACO Apachedefaultsettings' and
'AuthAzServiceDefaultSettings' are showing the following wrong syntax :
FCCForcelsProtected (Note the "L" lower case in the middle of the Parameter)
That should be replaced by the
FCCForceIsProtected (Note the "i" upper case in the middle of the Parameter)
note that in the first there's a lower case "L" instead of capital "i".