Need to input password on RHEL 8 while it shouldn't

[andy-yu-y]

Net::SCP.download!" is getting a password prompt for RHEL 8 hosts.
But if directly execute scp command to download the same file from the same host the password is not needed.
We already do below setting on the host:

1. copied id_rsa.pub to authorized keys to avoid password prompt
2. added config file to avoid HostKeyChecking prompt:
   Host *
   StrictHostKeyChecking no
   UserKnownHostsFile /dev/null
   LogLevel QUIET

Could anyone help to how to fix this issue?
We are using version v3.0.0