You can try to configure the GPIO matrix again, please note that this time you have to make changes in the GPIO configuration.
Thanks for the reply. If we configure the IOMatrix while the firmware is in active, then we need to reset our device, right?. Because only once we can configure the IOmatrix.
I got the answer. Initially I have configured the GPIO and after I completed my work, I have disabled this GPIO to get back the UART functionality by using CyFx3DevIOSelectGpio(55, CyFalse, CyFalse) function. Now it works fine.
Thanks abga_3064221 for your reply.