sslscan: 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/sslscan - from package: sslscan

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

On Debian possible default full paths are:

/usr/bin/sslscan - from package: sslscan

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

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