Raspbian (Buster) SSH issues

I use raspbian on a pi as a simple method to demo Duo. My (documented)config has worked fine over several versions of the stretch based version, but a recent move to buster has seen duo break. I’ve tested a fresh build and config on stretch (no issue), but I was wondering if anyone could shed some light on the following error in /var/log/auth.log:
Aug 4 15:10:14 pihost sshd[27813]: pam_duo(sshd:auth): conversation failed
Aug 4 15:10:14 pihost sshd[27813]: Aborted Duo login for ‘username’ from Error gathering user response
Aug 4 15:10:16 pihost sshd[27813]: Failed password for username from port 63820 ssh2

I’m using simple username/password. Config as per Duo Unix - 2FA for SSH with PAM Support (pam_duo) | Duo Security is correct (which is the basis of my documented config), and secrets/keys/url’s all work on stretch when the pi has the same ip address as the buster version of raspbian (so no firewall/DNS issues).

Thanks in advance

Hi @reevesc, thank you for sharing your question with the community! Our Duo Unix integration is one of the more challenging ones to troubleshoot and assist with I would say. I’m not finding anything conclusive that would help based on the error messages shared here.

For the fastest help with this issue, I recommend contacting the Duo Support team. They can take a look at your configuration and go from there.