could not ssh connect to database instance

Summary

could not ssh connect to database instance

Content

Hello.

I created two non-database instances and one db instance in the Oracle Cloud. I used the same public key.

Now I could login (with putty) to that two instances with user opc and private key.

I can't login the same way to db instance, got an error "Server refused our key".

If I open "SSH public keys" in Compute Console, I see, for some strange reason, 3 (three) public keys, one is my original key, bound to that two instances, that are OK.
And, one public key with the name: "dbaas.myservice.DB.ora_tools" and one public key with name "dbaas.myservice.DB.ora_users".