RAK811 RUI UART Receive not working

Issue: RAK811 RUI UART Callback not working

Setup: RAk811 Breakout board Lora module

Details: I want to use UART of RAK811 to send & receive data. And rui_uart_send function is working ok with both RUI_UART_NORMAL, RUI_UART_USER,RUI_UART_UNVARNISHED mode. But, Now i want to receive data too and rui_uart_recv function is not working with RUI_UART_NORMAL,RUI_UART_UNVARNISHED mode. and in RUI_UART_USER mode, it is receiving data but not come out of rui_uart_recv function.