Can you please explain more about your set-up? Have you tried bootoading with Bootloader host tool (along with USB-UART bridge) to confirm that the issue doesn't lie at PSoC 5 side?
Can you please attach the scope waveforms if possible?
The successful scope data for UART bootloading will be like the file attached. Please install Salear logic to view that file.
uartbootloader.logicdata.zip 44.4 K