if the activation dialog appears at every program start and you can only start the program by entering the serial number and email address, the following steps should be performed.
Rename or delete "installation_suite_prox8.ini" - (c:\ProgramData\Magix\Samplitude Pro X8 Suite).
Start program (Mxinstallhelper.exe is called automatically) and confirm Repair function.
Start the program again and enter Serial and Email address again -> Activation.