cnvgrib2to1: command not found

Have You tried accessing the binary with the full path?

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/cnvgrib2to1 - from package: python3-grib

You may install the required package with command apt-get install {package}
Error in other languages:
cnvgrib2to1: bevel nie gevind nie
cnvgrib2to1: comandă negăsită
cnvgrib2to1: comando não encontrado
cnvgrib2to1: commande introuvable
cnvgrib2to1: command not found
cnvgrib2to1: käsku ei ole
cnvgrib2to1: không tìm thấy lệnh
cnvgrib2to1: komanda nerasta
cnvgrib2to1: Kommando nicht gefunden.
cnvgrib2to1: kommandot finns inte
cnvgrib2to1: komut yok
cnvgrib2to1: nie znaleziono polecenia
cnvgrib2to1: níor aimsíodh an t-ordú
cnvgrib2to1: no se encontró la orden
cnvgrib2to1: no s'ha trobat l'ordre
cnvgrib2to1: opdracht niet gevonden
cnvgrib2to1: parancs nem található
cnvgrib2to1: perintah tidak ditemukan
cnvgrib2to1: príkaz nenájdený
cnvgrib2to1: příkaz nenalezen
cnvgrib2to1: команда не найдена
cnvgrib2to1: командата не е открита
cnvgrib2to1: 命令找不到
cnvgrib2to1: コマンドが見つかりません