I am using the latest captivate version.
When I try to preview my project it opens a broswer window that does not contain the usual localhost:xxxx/
2019 HTML5 Preview URL: http://html5temp8804310345721pre/index.html
2017 HTML5 Preview URL: localhost:9806/HTML5Temp7052315390622Pre/index.html
I tried adding "localhost:9806/" to the 2019 URL, but still did not get the preview.
My previews come up as localhost:49221/preview/HTML5Temp...
I am on 2019
Perhaps that might help in the short term...?
Might there be a firewall or antivirus rule blocking that port?
I have never personally seen this so it is just a thought.
This happened to some of the attendees at the Captivate Certification course last week in Las Vegas. It seems like the Adobe support folks who were there were having them create a blank responsive project and generating a "Live Preview on Devices," which then allowed them to preview their other projects using the "HTML5 in browser" option. I don't know why that worked but I thought I'd share it in case it works for you. Also, seems like the problem was happening in different browsers (Chrome, IE); I wasn't experiencing the problem so I wasn't paying close attention, but it happened to a number of other people at the event, so the Adobe folks should definitely be aware that it is a problem. Hope this helps!