Issue with Command Handling in AVR128DA48 UART Communication

I am using AVR128DA48 microcontroller to control an LED in serial communication. The way I set it up is not complex; I’m sending ‘ON’ and ‘OFF’ commands from a python script over UART to toggle the LED on the microcontroller. Funny how I am encountering an issue where the first command is ignored, but the second one triggers a response. Here’s what happens: - I send ‘ON’ – the microcontroller does not respond. - I send ‘OFF’ – it responds with ‘LED ON’. - I send ‘ON’ again !! – it responds with ‘LED OFF’. It makes me feel like the board is always responding to the previous command, and I don't know why 🥲. Normally I know microcontroller has simple firmware that reads serial data, processes the ‘ON’ or ‘OFF’ commands, toggles the LED accordingly, and sends back a confirmation message like ‘LED ON’ or ‘LED OFF’.
But what could be causing the delay or missed first command that I am facing? How can I ensure that the board processes the first command correctly and responds immediately? I made sure to verifying the baud rate and ensuring it matches on both ends as 9600 Even flushing the serial buffer before and after sending commands in the python script.