A problem to connect radio controller with apm.. COM3 isn't available

I have FlySky Radio Controller… I could bind it with its receiver successfully. However, Once they are connected together COM3 becomes unavailable. Thus, I cannot connect it to the computer using usb port… I need to do so to do the calibration for the Radio Controller… Thanks in advance

I would double check that your APM is getting sufficient power as maybe your USB port cant power the APM with all its accessories in addition to your receiver.

Also how are you connecting your receiver to the APM? A pic would be helpful.

I also tried connecting the all the signal wires and the power + & - only to CH1… It didn’t work… Maybe the receiver keeps COM3 busy? Is this how it works? I’m sorry if I ask basic questions… I’m still new at this. However, I have learned a lot of things in engineering that I want to apply using the quadcopter… your help is highly appreciated