Same as https://forums.bitfire.at/topic/2136/lists-syncing-contents-not? Can you provide logs? Without verbose information, we’re not able to say “why”.
Is there a possibility to define different ORGANIZER’s for different calenders on the same account or would you consider implementing such a feature?
Since Nextcloud supports invitations I use this feature more and more often. The pity is, that DAVDroid always uses the email address that I configured for the entire account and not different addresses for each calender (as Thunderbird/Lightning does). Since I have a few different calenders (personal, work, and and NGO where I am board member) I would like to use a different email addresses for each of them, since I have different mailboxes for each of those contexts.
The ORGANIZER is managed by Android (which uses the account name when no organizer has been set) and/or the calendar app. DAVdroid only takes the values which it receives from the calendar provider, see the image at https://www.davdroid.com/faq/system-integration/
You could create multiple accounts with various account names (= ORGANIZERS) and then use the calendars accordingly.