Solved the issue, it was owner and permission settings on the private key.  Stumbled across an article regarding file owner of the key getting error about permissions that does not affect a group owner's access to the file.  A chown and chmod resolved the issue.
Have a strange issue.  AVE 19.4 with DDVE 7.8.  System is a replication target.  Avamar Administrator and AUI show DD as red.  Also shows DD as having Full Access.  Replication group on the source successfully initializes and completes.  Have re-added keys per KB.  Can ssh with admin keys using to  No errors or warnings in ddrmaint.log.  Went through the AVI to install and run the SessionSecurityConfiguration avp.  No errors.  When I try to edit and save the DD in administrator GUI, I get the ssh client is not authenticates and it fails.  I am able to login to the DD with the credentials supplied, as admin.  I have been though postings and documents and cannot seem to solve the issue.   If this problem has been posted here or elsewhere, I cannot locate it.   Any suggestions? Regards
Ssh client is not authenticated