This happens due to the incorrect verification of installed Virtual C++ when uninstalling the old Deep Security Agent(DSA) during the upgrade process.
 
This issue has been observed on the following scenario: 
1.    Upgrading the DSA from version 9.6, 10.0 U3 or earlier version  to a later version.
2.    Upgrading the DSA for a second time. 
       For example, upgrading DSA from 9.6 to 12.0, and then upgrading DSA from 12.0 to 20.0 GM.
 
This issue won’t impact the protection provided by the latest DSA. And to resolve this issue, you can choose either of the following methods:
•    Uninstall both DSAs, then install and activate the DSA version you desire.
•    Upgrade the DSA for the 3rd time.
      For example, if you have upgraded DSA from 9.6 to 12.0 then 20.0 GM, upgrade DSA 20.0 GM to 20.0 latest build.