Hi Guys, I am a developer with Aero Ranger and came across your post. Great that you are trying our app, we are always keen to get feedback. There was a major update released a few days ago that gives more functionality, too.
The app has mainly been designed tested with the Mavic Pro, Mavic Air, M200 and Phantom range, as many functions rely on waypoint flying, which the Spark does not support. That means most of the missions won't work (Area Scan, Panorama etc) on the Spark. Of course there is nothing stopping you using the app and flying manually.
The new version gives you a lot more DJI GO style camera controls if you expand the live view window to full sized (that's now the initial default in our app). Even so, it appears that RAW is not supported by the Spark, we weren't aware of that until recently. The switch will be disabled for the Spark in future versions as it doesn't actually do anything!
We are working on a new mission style, which will allow some functionality for the spark (eg. for panoramas)
The image tag system you discovered works a bit differently. It doesn't take a photo, just scrapes an image from the live view and synchronises it with our cloud. That's why there was no photo to find. It's designed for inspections of buildings etc. Your app login details will work at the cloud
Aero Ranger Cloud if you want to take a look. You can see your tagged images there.
It should also be possible to take a photo in the normal way using the button on your RC controller or the on screen button on the new version of the app when the live view is full screen.
BTW I think your login issues were due to some back end problems we were having around that time. We have since fixed those. It should be possible to log in to the app once and not need to log in again, it will remember your details and log you in automatically next time.
Hope you enjoy the software
Regards
James