gpx2shp: 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/gpx2shp - from package: gpx2shp

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

Error in other languages:
gpx2shp: bevel nie gevind nie
gpx2shp: comandă negăsită
gpx2shp: comando não encontrado
gpx2shp: commande introuvable
gpx2shp: command not found
gpx2shp: käsku ei ole
gpx2shp: không tìm thấy lệnh
gpx2shp: komanda nerasta
gpx2shp: Kommando nicht gefunden.
gpx2shp: kommandot finns inte
gpx2shp: komut yok
gpx2shp: nie znaleziono polecenia
gpx2shp: níor aimsíodh an t-ordú
gpx2shp: no se encontró la orden
gpx2shp: no s'ha trobat l'ordre
gpx2shp: opdracht niet gevonden
gpx2shp: parancs nem található
gpx2shp: perintah tidak ditemukan
gpx2shp: príkaz nenájdený
gpx2shp: příkaz nenalezen
gpx2shp: команда не найдена
gpx2shp: командата не е открита
gpx2shp: 命令找不到
gpx2shp: コマンドが見つかりません