Why can't I register my Sigma? The webpage says the serial number is invalid.
Sigma serial numbers start with "si". For example, "si0987" would be a possible serial number. However, on the back of the unit, the "si" letters will be printed as capitals, such as "SI0987". One possible reason for a serial number to be rejected by the webpage, would befor the capital i to be misinterpreted and read as an L, and entered as such in the registration dialogue.
If you enter the serial number with the correct "si" letters and still cannot register, your unit, please contact Technical Support via "Ask A Question".