Not a PUBLIC member
You referred to a variable, property, function, or sub that was defined as a Private member of a class. Private members are not visible outside of the class to which they belong. For example:
Class MyClass
X As Integer ' X is Private by default.
Private Function Z As Integer
'...
End Function
End Class
Dim varV As Variant
Set varV = New MyClass
varV.X% = 10 ' Illegal: X is Private.
anInt% = varV.Z% ' Illegal: Z is Private.
Remove the reference or, if possible, change the definition of the class member from Private to Public.