My recovery pset4 solution recovers all 16 pictures, and I can see them. But in the gradebook I got 0 points except for the last image. Can I contact staff to get solution to my problem?
Not sure that you can get to "staff" or how soon, but there are lots of people here that can help you. Your problem is not unusual.
You say that the last file is the only one being produced correctly, although they are all being processed. Check how the code is processing the end of the earlier files and transitioning to the next file. Are you adding something extraneous to the end of the first 15 files?
Since the last one is right, it sounds like there's nothing left to process from the input, so it is closing correctly. The first 15 files are probably either getting something extra appended (likely), or are missing something when you close them and open the next. There are other questions on this. Review them and see if anything applies.
If you're stuck, post the relevant section of your code and maybe we can suggest a direction to go.
If you think this answers your question effectively, please mark it as answered. Let's keep up on forum housekeeping. ;-)