Hi edsev61,
Thanks for contributing to the Apple Support Communities.
It sounds like you can't play Audible files in iTunes for Windows or sync them to your iPhone 4 because the files are not authorized.
Have you recently updated to iTunes 12.2? If so, see the instructions from the Audible Help Center article How can I authorize my Audible account on iTunes 12.2?
For previous versions of iTunes see How can I authorize/activate my computer with my Audible account in iTunes on a Windows PC? or follow the steps in Get the latest version of iTunes to update iTunes to the latest version.
Since Audible is a separate service, your Audible account information may be different from your Apple ID (iTunes Store account information.)
If you're listening to Audible files on your iPhone, another option is to use the iOS app--https://itunes.apple.com/us/app/audiobooks-from-audible/id379693831?mt=8
Cheers.