Problem with SFTP on New 24.04 server

[Steve Matzura]

I have a server currently on 20.04 which has been regenerated by the 
service provider with 24.04. It's vastly different from 20.04--larger, 
for one thing, definitely faster. After receiving the "stock" instance 
from the provider, I began setting it up in much the same way as the old 
20.04 server. This included SFTP.


The first thing I noticed was that when I created the new system, I was 
not asked for an admin account. I see the default admin username is 
ubuntu. Perfectly fine.


I created some users and installed some applications successfully, 
including Wordpress, nginex, etc., but when I tried to set up the 
account for SFTP, that's when I ran into trouble. I didn't change 
anything in /etc/ssh/sshd_config other than adding some "Match User" 
lines at the bottom, and specifying secure FTP with the line:


SubSystem ftp internet-sftp


I also restarted the ssh process with:


systemctl restart ssh


All of the above worked OK.

When I try to SFTP into the acount I set up for this purpose, my SFTP 
client simply tells me "Error connecting to server," and I see nothing 
in /var/log/auth.log like I would expect to see for authentication 
problems. I do see lots of hacks and probes, but nothing specifically 
from my client's address.


If I try to ssh into the user account that I want to use for secure FTP 
and do it from the server itself, I get the error message "Permission 
denied publicly." Online research hasn't been very helpful. I found 
articles about setting up public/private key pairs and using ssh-copy-id 
to get them over to and installed into the target account, but when I 
execute


ssh-copy-id -i {the-key} {the-account at my-server}


I get the "permission denied publicly" error again.


Does all of the above mean I can't use ssh keys to access shell or GUI 
acounts and I have to go back to password authentication? I thought that 
might be the case, so I changed "PasswordAuthentication" from No to Yes 
in ssh_config, but that didn't solve the problem.


What am I missing?


TIA
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