Sometimes customers need to change their keys - common examples include:
Changing your crypto. ECC keys are faster and hence better for mobile devices, but RSA is more compatible.
Losing your private key
Creating a new certificate for the new public key is called 'reissuing'. Unlike other providers, reissues with CertSimple are free for the lifetime of the certificate. Just log into your orders page to set up the new keys and get a new cert!