wannier90.x: 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/wannier90.x - from package: wannier90

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

Error in other languages:
wannier90.x: bevel nie gevind nie
wannier90.x: comandă negăsită
wannier90.x: comando não encontrado
wannier90.x: commande introuvable
wannier90.x: command not found
wannier90.x: käsku ei ole
wannier90.x: không tìm thấy lệnh
wannier90.x: komanda nerasta
wannier90.x: Kommando nicht gefunden.
wannier90.x: kommandot finns inte
wannier90.x: komut yok
wannier90.x: nie znaleziono polecenia
wannier90.x: níor aimsíodh an t-ordú
wannier90.x: no se encontró la orden
wannier90.x: no s'ha trobat l'ordre
wannier90.x: opdracht niet gevonden
wannier90.x: parancs nem található
wannier90.x: perintah tidak ditemukan
wannier90.x: príkaz nenájdený
wannier90.x: příkaz nenalezen
wannier90.x: команда не найдена
wannier90.x: командата не е открита
wannier90.x: 命令找不到
wannier90.x: コマンドが見つかりません