you can always check if you have any open tmux session by typing:
tmux list-sessions
If there is one (or more) you can attach to latest session by typing
tmux a
if you have any frozen tmux session - you can kill it with:
tmux kill-server
before that, try to gracefully kill the cardano-node processes with:
killall -s SIGKILL cardano-node
if you are using CNtools scripts to run your nodes, after forced cardano-node shutdown (before it closes db and removes socket file) in some cases you will have to manually remove the socket file and only then start the script
Do you run your second node on the same server? If yes, then don’t forget to change in start script the db directory and socket file names so they are different from each node. It will not work if you are pointing to the same socket / db dir.