public key authentication not working? [3.38.1 on Win10]

[TinCanFury]

My first time trying to authenticate with this method. I've got my ppk file that I am using without issue with puTTY. When I try and use it through any of the three methods listed here,
https://wiki.filezilla-project.org/Howto
I get the same result, "Authentication failed."

If I log in with SFTP and use the password directly I'm able to log in fine.

I'm at a loss to figure out why it won't work. Does anyone have any ideas for me to try/check?

thanks!