plt-web-server: 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/plt-web-server - from package: racket

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

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