Git push fails in copied VM - stumped

I have been working on a codebase in a linux virtual machine on one system, and have been able to use git to clone/pull/push successfully on a remote repository.

I exported and copied this VM to another physical system and made some more changes to a branch, but I am unable to push it to the remote. I double-checked ssh-agent, made sure the correct key is loaded, but nothing works.

The error is

Connection closed by nnn.nnn.nn.nnn port 22
fatal: Could not read from the remote repository.

Please make sure you have the correct access rights
and the repository exists.