SanDisk iXpand™ Flash Drive for iPhone and iPad

hi how are you? i was wondering if you could help me out with my ixpand. i bought it a couple of days ago and it worked fine. i was able to copy my camera roll to the device and even managed to watch video from the device on my iphone. however, i used it until the battery ran out and it told me to charge it. i connected it to my computer and left it to charge until the green light showed up and after that i tried to use it again and my phone will not recognize it. when i open the app it tells me to check that the drive is charged and it is and a light starts to blink as soon as i plug it into the phone. dont know that that light means! the manual says that it means its tranfering files but how can it be that if i cant even see whats on it? on my PC i cant open it to see the contents either. it shows up as an external drive but when i click it it says to connect a drive. i really hope you can help me to fix this problem since i just bought it and only used it once.