Lighting with GoDaddy

[kgb71]

Thunderbird 45.1.0
Lightning 4.7.1

I would like to add a remote calendar to Lightning that is hosted on caldav.secureserver.net (i.e. GoDaddy).
I have tried the same URL that works on my phone...

https://caldav.secureserver.net:8443/principals/users/user@server.com/#######

...where user@server.com is my user ID, and ####### is the calendar ID.

I am prompted for my user name and password when I add the remote calendar.

The calendar appears with an exclamation point inside a yellow triangle, and the message "The calendar MyGodaddyCalendar is momentarily not available."

I see the following in the Error Console:

Warning: There has been an error reading data for calendar: MyGodaddyCalendar. However, this error is believed to be minor, so the program will attempt to continue. Error code: DAV_DAV_NOT_CALDAV. Description: The resource at https://caldav.secureserver.net:8443/principals/calendar/user@server.com/####### is a DAV collection but not a CalDAV calendar

I have tried several variations of the URL (based on web searches), but to no avail.

I have contacted GoDaddy about this, but they dismiss the issue saying Thunderbird/Lightning are not supported.

Has anyone has success in adding a (synchronized) GoDaddy calendar to Lightning, and if so, what did the URL look like?