RS485 in Arduino FreeRTOS

I am working on a project wherein P10 LED matrix display has to numbers received from MODBUS RTU as well as numbers in Arduino EEPROM.
I have used FreeRTOS for this purpose. Here one task is for EEPROM, here display will show numbers stored in EEPROM and 2nd task is for serial reception over MODBUS RTU and display on P10. Default task is of EEPROM.

I am facing problem is that when I use RS485 MODBUS for serial reception, it is not working. (Reception and display activity). However if I use Arduino serial port for same task, it is working. (i.e. it is receiving serial data as well as showing numbers in EEPROM at regular intervals)

Can anyone help me to resolve this issue?

Below are the details of my hardware & software

Board : Arduino Uno
IDE : 1.8.16
FreeRTOS version : 10.4.4.2
Libraries used : EEPROM, Arduino FreeRTOS, DMD, TimerOne

Which MCU are you using?