Hi,
Thank you for posting in Symantec connect.
I would be glad to answer your query.
Previously we used to download the latest software from https://fileconnect.symantec.com Now It has been changed to https://symantec.flexnetoperations.com.
Currently old URL is redirecting to the new one.
On the flexnetoperations you will find only the latest version of SEP.
SEP 12.1 RU3 (12.1.3001.165) is the latest version of SEP.
There are two versions i.e. SEP 12.1 RU2 (12.1.2015.2015) or SEP 12.1 RU2 MP1 (12.1.2100.2093).
You need exact the same version to complete successful repair.
You must have downloaded the setup while doing install of SEP 12.1.2, Do you have that setup with you? If yes, please go ahead and repair with that.
If not then request the support team to upload the required version on the FTP server for you.