I would start by going to your native photos app and see if the pictures can be deleted from there. If so can you provide some more info so we can try to isolate the issue?
What version of the iXpand do you have? Click here to see the different version of the iXpadn USB flash drives
What App version and FW version are you using?
How many pictures are you trying to delete?
What iOS device are you using?
What version of iOS are you using?
The more info you can provide will be helpful in trying to find a solution for you.
