plsense-server-main: command not found

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 Debian possible default full paths are:

/usr/bin/plsense-server-main - from package: plsense

You may install the required package with command apt-get install {package}

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