Before starting a reissue, you will need to generate a brand new CSR/RSA pair and save your RSA for further installation.
If you are not able to generate a CSR yourself for some reason, please ask your web hosting provider to do this for you.
Once you have a new CSR ready, you may proceed with the next step. Reissuance is completely free of charge unless you are adding SAN names to a Multi-Domain certificate with a reissue.
Note! Starting from June 23d, 2016, any Comodo SSL certificate can be reissued for a different domain. Please keep in mind that the previous (parent) certificate gets revoked in this case.
If you are reissuing an OV/EV SSL, use the same contact information that you used originally unless you are reissuing the certificate to change this information. This will save you some time during reissuance process.
Let's start with the process itself:
To request a reissue for a certificate in your account, please click on small arrow on top black bar with your username -> choose 'Purchased certs'
Click on the 'Active' status of the certificate you want to re-key and choose the 'Reissue (new private key)' option.
Copy and paste the CSR code generated for the certificate reissue.
Select the server type the certificate will be installed to.
Choose the domain control validation method for the reissue, either one of the approver email addresses or uploading a text file.
Confirm or change administrative contact information.
Note: You will not be able to change administrative email address during the reissue process. The reissued certificate will be sent to the same email that was chosen during the original certificate activation.
If you need to change the approver email address for the domain ownership verification, please contact our support team via Live Chat or ticket system.
After the certificate is validated, the certificate files will be sent to the SSL administrative email. Do not forget to install a new certificate on the server replacing the old one.