SSL reissue means your certificate will be replaced by a new one.A reissued SSL certificate is only valid till the remaining time on the original certificate.You can request a reissue only for the same domain name as mentioned on the original certificate.

To request a reissue for RapidSSL, RapidSSL Wildcard, QuickSSL, QuickSSL Premium, True BusinessID with EV certificates, please visit the link below:

https://products.geotrust.com/geocenter/reissuance/reissue.do

To request a reissue for Comodo Premium, InstantSSL,PositiveSSL and PositiveSSL Wildcard certificates, please login to your Namecheap account and goto Your SSL certificates page. You will find a reissue link next to the certificate.