tblcvt: 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/tblcvt - from package: troffcvt

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

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