Some users report having the following error when testing their forms online: 

Error: Unregistered user or invalid serial number or e-mail !
Erreur: Usager non enregistré ou numéro de série ou courrier électronique non valides!
Unregistrierter Benutzer, ungültige Seriennummer oder E-Mail
Fout: niet geregistreerde gebruiker of ongeldig serienummer of e-mail !
Error: usuario no registrado o número de serie/dirección de correo electrónico incorrectos.

This message means that the information in the project properties doesn't match validation information for the form, or the form was not properly configured. 

Please find below the detailed procedure to install the Dataform security update and validate your forms: 
1) Install the update (if you don't see a validation section in the form property box)
2) Open your project
3) In the form properties, add your serial number and registration email
4) Regenerate your project
5) Upload your project on your FTP again: the complete website, A PARTIAL UPDATE WILL NOT WORK

There is no other possible cause for this error, follow the procedure exactly to resolve this issue.