How do I reload TMUX configuration?
tmux.conf is the configuration file for tmux. You are not supposed to source it within your shell, but rather tell tmux to source it.
Any of the following should work:
run
tmux source ~/.tmux.confrun
tmux set -g prefix C-apress the old prefix (CtrlB),
:source ~/.tmux.confpress the old prefix (CtrlB),
:set -g prefix C-a