ROV switch on just plug in the batteries and without connecting the usb



I completed the construction of the rov and everything seemed to work perfectly, but today something strange has happened. From now on, my ROV comes on just as I plug the batteries into the tubes, even just filling up a tube so that it starts. Booting with the USB that is connected to the tent does not work anymore. You know what happened and what can I do ??? It could be a software issue.
I also have another small question when I’m in Cloud9 and try to modify the code after making my changes except (ctrl + s) and running in run, but I get an error about the non-presence of the Arduino.h library in folder. in fact, checking in all folders I could not find the Arduino.h library.
What is this error caused? What can I do? Help me please