Recreating new SSL commercial certificate

[dhawal]

Respected SIr,
i have one issue regarding SSl certificate installation, i have one client whose commercail certificate had expired so i have installed self signed certificate for temporary use and it is working perfectly. But when i installed new commercial SSL certificate by creating .csr certificate and getting new SSL.ca and root.ca from client it showing error like invalid private key and all that. so please guide me what to do now.