Hi I have a 2 batteries that are 3.6 V each . the battery pack takes 2 batteries so that's 7.4 V total. so pretty much i have it hooked up to the VIN and GND pins but when I try to hook it up it doesn't power it on the boards , What can be the problem ?
Check the battery voltage, before and after connecting it to the Arduino. Also, be sure that the polarity is correct.
did you connect them in series or parallel?
or sometimes the connectors of the battery pack are faulty, check if power is received on the connectors end.
This is not the sort of question that can necessarily be answered in words, but a perfectly focussed picture of the apparatus taken in bright daylight but not sun might just reveal a clue.