SSH Agent with Navicat—Again

I can't get a database connection with SSH tunneling to work in Navicat Premium Essentials 16 working. I read up on https://1password.community/discussion/129678/ssh-agent-with-navicat and followed the tips from the last post, but it doesn't work.

Specifically, I'm trying to connect to an RDS instance on AWS. We have a bastion server (EC2 instance) set up, and I can SSH to that with the 1Password agent just fine. But when I create a connection in Navicat, I get an error:

Private key import failure. (28)

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1Password Version: 1Password for Mac 8.10.26 (81026039)
Extension Version: Not Provided
OS Version: macOS 14.3.1
Browser: Not Provided