I haven't had a chance to try this on the sky, but here are some additional pieces of infromation - which may or may not be of help to trouble shoot.
Nikon D5300, no shutter release cable, connected to USB 2.0 (tried USB 3.0 with the same result)
Preview mode: set exposure to 30sec. First exposure triggered the camera, downloaded, and displayed correctly.
Second attempt of a 30sec exposure failed; no triggering of the camera shutter, but AA+ happily counted down 30sec and tried to load the image. The same happened with additional exposure attempts.
Turned power to camera OFF/ON, and it worked, but only for the first exposure. Disconnecting the camera in AA+ does not help. Autorun does not work once it has failed an exposure in Preview mode.
When I connect a Nikon D7000 it is recognized as Nikon D7000 (PTP mode) in AA+. When connecting the Nikon D5300, it only says Nikon D5300. I'm using the Nikon mini-USB cable to connect the D5300 to AA+.