Run Debian 9 issue

Dear All,

We did install duo unix version.We are using debian 9. We have completed all steps. We want to use duo software with ssh. We get error connecting to the server. I added error is as follows. What is problem?Are installation steps correct?What should we do for this error? Thank you.

Regards.

Duo Server IP address: 10.1.1.152

Error:

root@adarguner:/home/adarguner/.ssh# ssh adarguner@10.1.1.152
adarguner@10.1.1.152: Permission denied (publickey).
root@adarguner:/home/adarguner/.ssh#

Regards