Thanks for the post.
Your report has been forwarded to the admins of the download site.
There are also other customers reporting the same issue.
I'll update this threat when the issue is resolved.
I just recieved confirmation that the CityEngine Trial download issue was fixed yesterday
and the downloads now seem to be working for me.
If it still doesn't work, it is recommend to clear the cache from your machine and retry.
In case you still see this issue, please send a screen shot and steps to reproduce this error.
Please excuse this delay and try out the new version of CityEngine:
I switched from Chrome to IE11 and got past the captcha screen.
It could be browser-specific, or maybe the absence of ESRI/Arcgis cookies in my IE11 gave me a clean start.