seems something is wrong with your OpenVINO installation. The file plugins.xml should be located at "C:\Program Files (x86)\IntelSWTools\openvino_2021.1.110\deployment_tools\inference_engine\bin\intel64\Release\plugins.xml"
It is part of OpenVINO binary package and not the result of Open Model Zoo demo build.
Thanks for reaching out.
When we tried out from our end, it worked without these errors. Can you please try to run the demo_security_barrier_camera.bat demo? Did you get the same error?
If so, the issue might due to incomplete OpenVINO installation and you will need to reinstall and make sure to follow all the installation steps carefully.
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