tcprulescheck: 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/tcprulescheck - from package: ucspi-tcp-ipv6
/usr/bin/tcprulescheck - from package: ucspi-tcp

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

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