Problem uploading code to Arduino Nano

I have an Arduino Uno and an Arduino Nano. I'm using both of them as transmitters and receivers(via nRF24L01). I had problems while uploading the code when I had only Arduino IDE 1.8.9(latest), but when my shopkeeper told me to download Arduino IDE 1.8.0 the code uploaded to Arduino Uno but then too it is not uploading the code to Arduino Nano.
What should I do?

Select Tools > Processor > ATmega328P (Old Bootloader) and then try uploading to the Nano again.

pert:
Select Tools > Processor > ATmega328P (Old Bootloader) and then try uploading to the Nano again.

I tried but it doesn't work.
Sorry, I looked up into this and the problem was that the port was selecting. So, I had to install the CH340G driver for it to work.

Thanks for taking the time to post an update B1aziken. I'm glad to hear you got it working. Enjoy!
Per