@lkeyes @robnicholson Those emails were sent to admins who had created a directory sync configuration but then did not actually configure any groups in the sync. We are sorry for any confusion this may have caused (feedback showed that some admins did not recall creating the syncs with incomplete configuration in the first place).
If you aren’t using those syncs and have no plan to complete setup for them, you should delete them.
These emails are unrelated to the OP’s posted issue. Using the connectivity tool is a good suggestion, so thank you @lkeyes! However, if the issue is with authentication to AD the connectivity tool output is likely to show the same auth failure already shown in authproxy.log.
@sindreh There are some suggestions you can work through in this KB article: Why were my Active Directory server credentials rejected when configuring Directory Sync?. If these don’t help you resolve the issue feel free to contact Duo Support for 1:1 troubleshooting.