html2xhtml: 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/html2xhtml - from package: libhtml-html5-parser-perl

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

Error in other languages:
html2xhtml: bevel nie gevind nie
html2xhtml: comandă negăsită
html2xhtml: comando não encontrado
html2xhtml: commande introuvable
html2xhtml: command not found
html2xhtml: käsku ei ole
html2xhtml: không tìm thấy lệnh
html2xhtml: komanda nerasta
html2xhtml: Kommando nicht gefunden.
html2xhtml: kommandot finns inte
html2xhtml: komut yok
html2xhtml: nie znaleziono polecenia
html2xhtml: níor aimsíodh an t-ordú
html2xhtml: no se encontró la orden
html2xhtml: no s'ha trobat l'ordre
html2xhtml: opdracht niet gevonden
html2xhtml: parancs nem található
html2xhtml: perintah tidak ditemukan
html2xhtml: príkaz nenájdený
html2xhtml: příkaz nenalezen
html2xhtml: команда не найдена
html2xhtml: командата не е открита
html2xhtml: 命令找不到
html2xhtml: コマンドが見つかりません