Are your long running ssh agent sockets failing? Perhaps something is cleaning /tmp? This rc file for ssh fixes all these problems.

Fix ssh sockets in Tmux

# Fix ssh sockets so they always work in Tmux/Screen, even after you re-connect dmcanulty 2021
#
# After putting this file at ~/.ssh/rc     add the following to your  ~/.bash_aliases
#      alias ssh="SSH_AUTH_SOCK=~/.ssh/ssh_auth_sock; ssh"
#      alias git="SSH_AUTH_SOCK=~/.ssh/ssh_auth_sock; git"

# If the symlink does not point at a valid socket, and the env variable is a valid socket, make a symlink
if [ ! -S ~/.ssh/ssh_auth_sock ] && [ -S "$SSH_AUTH_SOCK" ]; then
    ln -sf $SSH_AUTH_SOCK ~/.ssh/ssh_auth_sock
fi


################
## Extra tips ##
################
# 1. If your using my older get-ssh-sock.sh/fix-ssh-sock scripts and you want this to work
#    (without restarting everyting), remove the .bashrc entries and comment everything out
#     in the fix-ssh-sock script and then add the following line to it
#         export SSH_AUTH_SOCK=~/.ssh/ssh_auth_sock
#
# 2. If you like to have multiple Putty sessions open at once:  connection->ssh->Share SSH connetions
#    This will prevent issues with one session stepping on another, if you close 1 they all go down.
#
# 3. If your starting your tmux adcentures from scratch, instead of using the alias entries above you can
#    instead add the following to your .tmux.conf file
#         set-environment -g 'SSH_AUTH_SOCK' ~/.ssh/ssh_auth_sock