If your Serial Number has changed, you will need to update this in the Calxa App.
Open Calxa and then click Activate on the main ribbon:
Choose Internet Activation, then it will be operational immediately, and click NEXT:
This card will appear, the existing details will be in the form, you can just copy the new Serial Number from the email and paste into this box, and overtype other details as necessary.
Confirmation screen will appear, click CLOSE and you should be able to continue with Calxa.