It is just me or has access to the multiple purchase options for the Eberron content been closed off?

They still appear for me. Are you looking at the new Eberron book (Eberron: Rising From the Last War) releasing in November, or Wayfinder's Guide to Eberron? 

Wayfinder's.  It wasn't showing up in Marketplace when I clicked on that button.  Which route did you take to get to it?

Also, do you know the main differences between the two books?

I went to the Marketplace and Ctrl+F to find Wayfinder's, it appears to be at the end of the Sourcebook list. 

I don't know anything beyond what has been announced or discussed by the designers on Twitter. I'm looking forward to learning more!

Thanks.

Now I'm wondering whether I should wait for Rising From the War to drop so that I know what's in it before purchasing the Wayfinder book.