Automatic camera upload not working after uploading 7 files.

Hey, it's been two years so I'm sure you've sorted it by now but answering in case it might help someone in the future too.

I also got stumped by this. I went to the settings to look at clearing the cache as advised earlier (still have no idea how to do that lol) and in the settings I saw that I had only given Dropbox limited access to my photos. I switched this to full access and everything in my cameraroll started backing up straight away just as planned. 

Hope this helps!