Error when reading options

I am receiving errors when trying to use the Modern UI macros to read the options.

I have a custom page the page displayed correctly via:

  ; Display the import page
  !insertmacro MUI_INSTALLOPTIONS_DISPLAY "Update" 

The page is some text (Field 1) with several check boxes (Fields 2-6). If I compile this it displays the page perfectly.

Trouble begins when I try to read the options:

  !insertmacro MUI_INSTALLOPTIONS_READ $CopyConfig "Update" "Field 2" "State" 

This causes the compiler to throw a wobbler with the messages:
Error in macro INSTALLOPTIONS_READ on macroline 2
Error in macro MUI_INSTALLOPTIONS_READ on macroline 5
Error in script "C:\dev\installer\test.nsi" on line 96 -- aborting creation process

I've followed the examples here and here. What am I doing wrong?

Perhaps you are missing Var CopyConfig. Just use one of the pre registered variables $R0-$R9 and $0-$9 to save on memory use.

Stu