According to their instructions, you should be able to add a CalDAV calendar (File/New/Calendar..., On the Network...) by adding your flock.com address as the username and https://dav.flockmail.com as the calendar server URL.

I don't know if this works, but they say:

"However, if you are facing any difficulty in configuring CalDAV do let us know at support@titan.email, we would help you in every possible way!"

Thanks for the quick response. However, I still have not resolved this issue. The Titan article you referenced tells how to use CalDAV to sync Titan calendars to the Windows, Mac and iPhone operating systems, not specifically to apps such as Thunderbird. The one piece of pertinent information I got from the article is that their CalDAV server's URL is https://dav.flockmail.com.

My efforts had already lead me to think that the way to sync Titan calendars to TB is with CalDAV and that the way to do that in TB is by using the TbSync add-on. My attempts to use TbSync and their FlockMail server URL have all failed.

I am also corresponding with Titan support but their initial response missed the points entirely and I'm waiting for another response. As of now, I think there is either a problem with their CalDAV server, or with TbSync, or possibly I'm just not understanding what needs to be done.

What would really be helpful right now is to hear from somebody who has had first-hand experience in syncing Titan Calendars to Thunderbird.

Any further suggestions?

The TbSync site doesn't mention Titan support, but that doesn't mean you can't (or can) add a Titan calendar using the built-in option, without TbSync. What happens if you add it as mentioned above (File/New/Calendar...)?

I'm setting this aside for now. Will pick it up later. Thanks.