Hope you using CYUSBS232 DVK. Is the USB serial configured to CDC mode using cypress serial configuration utility. If not configured you can download USB serial SDK and you can find the config utility in the following path.
C:\Program Files (x86)\Cypress\USB-Serial SDK\bin
To configure the device in CDC mode refer to the utility guide in the following path
C:\Program Files (x86)\Cypress\USB-Serial SDK\bin\Documentation
Once the device is configured it will appear under the ports in the device manager along with "USB UART LP Vendor MFG"