How to copy dropbox data from the old 1password windows app to 1password.com.

I had the exact same problem. I don't think the import process works with version 8 at all (or at least I could not find it). Luckily I noticed something about version 7 on the help article, so I gave that a try.
1. First I unistalled version 8.
2. then installed version 7 from https://1password.com/downloads/windows/, under "Using an older computer" section.
3. Then I opened my 1password file from drop box. This prompted me to change the file type and archived the old version.
4. Then I logged in to my cloud 1 pass by clicking "buy 1password", which took me to a log in page. I had already setup a new cloud account.
5. Once logged in it prompted me to import everything to the cloud.

This all worked well, but its crappy that 1password doesnt make this work natevly in 1pass 8.