It asks an admin prompt. So inside an admin cmd.exe, it fails with:
certutil.exe -importpfx Root mitmproxy-ca-cert.p12
Entrez le mot de passe PFX :
CertUtil : -importPFX ÉCHEC de la commande : 0x80092007 (-2146885625 CRYPT_E_SELF_SIGNED)
CertUtil: Le certificat spécifié est auto-signé.
I use a blank password, is that right ? If not, what is the password ?
How old is your <your user folder>/.mitmproxy folder? If you created your root certificate authority with an older version, can you delete ~/.mitmproxy and try again?