tmux-top: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/tmux-top - from package: tmux-top

You may install the required package with command yum install {package}
Error in other languages:
tmux-top: bevel nie gevind nie
tmux-top: comandă negăsită
tmux-top: comando não encontrado
tmux-top: commande introuvable
tmux-top: command not found
tmux-top: käsku ei ole
tmux-top: không tìm thấy lệnh
tmux-top: komanda nerasta
tmux-top: Kommando nicht gefunden.
tmux-top: kommandot finns inte
tmux-top: komut yok
tmux-top: nie znaleziono polecenia
tmux-top: níor aimsíodh an t-ordú
tmux-top: no se encontró la orden
tmux-top: no s'ha trobat l'ordre
tmux-top: opdracht niet gevonden
tmux-top: parancs nem található
tmux-top: perintah tidak ditemukan
tmux-top: príkaz nenájdený
tmux-top: příkaz nenalezen
tmux-top: команда не найдена
tmux-top: командата не е открита
tmux-top: 命令找不到
tmux-top: コマンドが見つかりません