HPXcvt: 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 CentOS possible default full paths are:

/usr/bin/HPXcvt - from package: wcslib-utils

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/HPXcvt - from package: wcslib-tools

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

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