I have a HC-05 module which works absolutely fine with an Arduino Uno. Because I need to reduce the size of it, I tried using an Arduino Nano.
After correctly wiring it up to the Nano, sometimes the LED doesn`t turn on, or sometimes it does not appear in the devices listing of my smartphone. It also resets randomly the Arduino. I have tested it and it fully works without any problems with the Uno.
I think it is a power issue, but not from my computer or any other computer because I tried on all my computers.