If your scp fails with a Connection closed message, then add a -v to your options,
scp -p -v myfile.txt user@host:/home/user/Downloads/
to see if you get something like the following:
debug1: Sending subsystem: sftp debug1: client_global_hostkeys_private_confirm: server used untrusted RSA signature algorithm ssh-rsa for key 0, disregarding debug1: update_known_hosts: known hosts file /home/xmas/.ssh/known_hosts2 does not exist Connection closed
If you see the Sending subsystem: sftp message, then there is a discrepancy between your versions of ssh. Until you get them all up to the same level, where they are using sftp, add -O (dash Oh) to your scp options to override and use the old way of transfer. You can find more information on -O in your system's man pages.
-O Use the original SCP protocol for file transfers instead of the
SFTP protocol. Forcing the use of the SCP protocol may be neces-
sary for servers that do not implement SFTP, for backwards-com-
patibility for particular filename wildcard patterns and for ex-
panding paths with a '~' prefix for older SFTP servers. This
mode is the default.