My wish list is not accessible any more. Any ideas why and how to fix it?

See the 'View, purchase, or remove items from your wish list' section in:

Create a wish list in iTunes on PC - Apple Support

Are you signed in with your Apple ID? If so, you may need to re-authorize your computer.

The wish list would be in the "Account" tab in the upper left.

I hope this helps answer your question. :-)

-Casey Black