Did an in place install of DevTest 10.4 on 10.3 and the InsightAgent.jar is used from 10.3. Agents show "upgrade agent version" message in the DevTest Portal.
Started the carsdemo application from DemoServer\carsdemo\start.bat.
Demoserver is installed manually by extracting the DevTestDemoServer.zip outside the DevTest folder and start.bat-->Line 37 set DIRNAME as below which caused the issue:
. set DIRNAME=%~dp0
If the DevTestDemoServer is installed with DevTest itself then the DIRNAME is set as below:
Recommended to have the DemoServer folder inside the DevTest_Home folder or change "set DIRNAME" line 37 in DemoServer\carsdemo\start.bat to the correct path.