If You are going to create Your own ReFill, make sure that You do some planning and organizing before You start creating any patches. Begin by creating a main folder on Your hard drive, a folder that will be the actual ReFill. Then add subfolders in this that will contain the samples or patches if You want to organize these in this fashion. Move the samples to their correct location in this main folder/subfolders before You start creating any patches. When the samples are in place, You can proceed with the actual creation of the patches. Be sure to save these patches inside the main soon-to-be ReFill folder. If You move anything afterwards, be it samples or patches, the search paths will be broken and the ReFill packer will be unable to create the ReFill.
When You edit the samples, save these with the proper file extension - .wav or .aif - even if You are on Mac system.
If any samples have migrated from one system to another, make absolutely sure that the file format is correct afterwards. We have seen that samples that e.g. have been created on a PC, saved as aiff files and then moved over to a Mac, could appear as AIFC files on the Mac system. The AIFC format is a compressed AIFF file and cannot be recognized by Reason. If this happens You have to convert these files on the Mac, either by using a conversion utility or by simply changing the Creator-type, using e.g File Buddy. Stick to one file type, it doesn't matter at all to the end result if the files are .wav or .aif - when the ReFill has been successfully created it can be used on either a Mac or a Windows system.