1) Please ensure that correct pins to the device. by default this project is for PSoC 4, for PSoC 5LP change the pins to the following:
2) Ensure that you are using the correct driver for the project. If you are using USBFS_UART.inf file from the project root directory as a driver then make sure you are using the default VID and PID for the project.
If this does not resolve the issue, kindly attach the project so that we can have a look at it. This will help us in getting better insight of the issue.
The USBUART component is an application of the USBFS component. This is the reason why the datasheet of the USBUART points towards USBFS component datasheet. The USBUART is used for implementation of communication device class (CDC) application. Please refer to the USBUART (CDC) section of the USBFS component datasheet for more details on this.