I recall I used to be able to bypass the preview, like Timothy's saying, but I'd recheck the manuscript as a precaution in the future if you're able to do that.

You can try deleting your cache and retrying. Just realize many of your passwords are in your browser and you'll have to re-enter them for access. Depending on your system, you can usually do that through your browser settings.

It could be a new year engineering snafu that Amazon's trying to work out. Or maybe, there's a glut of entries right after Jan 1?

Would love to be able to bypass the preview if you can remember how you did it.
I did try using the previewer to check the manuscript but ended up with the same problem. 
I had the same problem trying to make changes on a book quite some time ago and gave up, so I don't think it's a brand new change.
I have had the lost passwords story previously - and I'm on a LOT of websites so deleting the cache would be a last resort. 

Congratulations to your family! Looks like you had a wonderful day.

Normally you can keep going without that completing? Have they changed that?

Alternately, I'd try regenerating the page, and see if it resets or needs to be started again. The process might have hung, so restarting it might work better this time.

On the other hand, they may have changed something on the back end, and it's slowing everything down.

I've tried that a few times over a few days. When I click on 'save and continue' it goes into the generating preview mode - and sticks there.  Emailed KDP but they don't use that email address anymore

Ended up with a 'chat' on KDP. They say it's a browser problem and to try a different browser. Sent me a You Tube link that explains how to get rid of browsing history and cookies. Not comfortable doing that without consulting my technician as I'm likely to stuff up something important. 

I only seem to have Chrome as a browser.

I made a small change to my blurb and changed the categories on one of my books. I did NOT change the manuscript or cover. I did not request a preview, but I can?t save my changes as I have been stuck in this mode for two hours.

Generating your Preview...
KDP is processing your manuscript and book cover. This requires a number of steps and can take several minutes.

I also tried it two or three times a few days ago with the same result and had to give up. Is there a way to solve this problem as I am anxious for the changes to go through? I have sent an email to KDP, but thought someone here might have a quicker answer.
I've thought about launching the previewer, but am worried that I could bring more problems 

That's fascinating, since I read now and I have always read to be alone in a different world from my reality.

Could I be wrong or don't most writers write to escape into a different world, readers following after?