Some phone cameras don't re-orient images before saving them, meaning that images can be saved rotated, but with metadata specifying the rotation, so that image viewing programs can display them correctly. See here for details: https://www.howtogeek.com/254830/why-your-photos-dont-always-appear-correctly-rotated/

The cloud API appears not to take the rotation metadata into account, so it will fail to identify license plates that would be found if the image were correctly rotated. I was able to fix this in my client by simply rotating the image as needed before uploading it (using sharp), but it would be nice if the API could handle this for me.