Cannot subscribe to calendars from two accounts in Thunderbird Lightning?

Cannot subscribe to calendars from two accounts in Thunderbird Lightning?

We would like users to be able to have calendars in two accounts--a personal one, and a companywide one for common events.

I created both accounts, and after subscribing to my personal calendar, I tried to subscribe to the company one.  However, as you subscribe to it in Thunderbird, it is unchecked and grayed-out.  I am never offered the chance to enter a password.

I thought this was strange but decided to test it on a second computer.  There, I subscribed to the company calendar, and it worked!  But then, when I tried to subscribe to my personal calendar, I got the same result as for the company calendar on the other computer:  the calendar instantly unchecks itself and will not display.

The message in the error console is:
[calCachedCalendar] replay action failed: null, uri= https://calendar.zoho.com/caldav/67bec26b457998b7f4ff3aa462e24fdbde3fc8efc8d02811c461741fc9e90bb99cae46c3a4588ad05678a25ae599d81f/events, result=2147500037, operation=[xpconnect wrapped calIOperation]

So it seems like calendars from the first account which are added work, but those from a second account do not?  I do have the "calendar.network.multirealm" setting in the config editor set to true.  Is there any way I can get calendars from two Zoho accounts to show in the same Thunderbird Lightning at the same time?