Copied from my thread here:

https://forums.adobeprerelease.com/ccda/discussion/112/unable-to-log-into-acrobat-document-cloud#latest

"I'm at a McDonald's playing around on my Windows 10 laptop. I launched Acrobat, but wasn't signed in. Tried to sign in using the link at the top-right of Acrobat, the CC beta app launched and I went through the motions of signing in. It said I could now use Creative Cloud, etc. Returned to Acrobat, and still not logged in. I wanted to look at some documents stored on DC, but clicking on the left menu link also gave me the requrest to log in.

I was using Drop 1 at first. I went on the prerelease site and noticed the update for Drop 2, so I installed it, and still the same issue.

Other Adobe apps seem to work fine."

At the request of Vimal Varshney, here is a link to the result of the log collection: https://adobe.ly/31bd1L5

Hope it helps!