A couple of options, you can reset the secret phrase which will delete the details on the server allowing you to start over again. For details of how to do that see the Firefox Sync troubleshooting and tips article.

The secret phrase should be stored in the password manager of the Firefox version that you originally set up Firefox Sync with. Open the Options/Preferences dialog (for Windows, in the Tools menu select Options). In the Options dialog go to the Security panel and click on the "Saved passwords" button to open the password manager. In the password manager click on the "Show Passwords" button and in the search field type chrome, that should show your secret phrase.

Thanks for your reply, TonyE. My Password Manager didn't show me any info on my missing secret phrase (see attached) and I couldn't edit my secret password as outlined in the referenced article (see attached). I must have done something wrong in my first attempt. I started at the shown option page and went to the login for Sync...when I got to the subsequent secret phrase window there was an option to "change secret phrase" and I used that to reset. Hope this info will help anyone else who has a problem...

So I figured this out. The above post left out one important detail.

I did not have the reset sync key option on the enter sync key page. I entered some random numbers in the sync key field, then hit next. I then got the option to reset the key.

Starting with the Firefox Sync 1.5 version, the "Secret Phrase" is now known as the "Sync Key ".