Hi Varun,
The version of CA Patch Manager is found in file C:\Program Files\CA\UPM\build.txt
For UPM 12.8 this file should contain these lines :
CA Patch Manager r12.8
Build 12.8.0.77 (201312201021R)
Installer I201312201021R
Check if this file contains these lines. Otherwise update the file with these lines and try again the upgrade.
Thanks.
Jean-Yves