Hello Rue,
I think I have finally figured out the source of the issue. You have added NEF files to the project, but PhotoScan doesn't support Nikon RAW format, instead of that the preview images 160x120 pixel were added, so it's expected that such low resolution images cannot be aligned.
I can suggest to convert the images to TIFF format, for example, and then reprocess together with the DJI data. Also I've noticed that the EXIF information for drone images is lost, it may happen if you were preprocessing the images in the external image editor or used video frames, so I also recommend to input known focal length and sensor pixel size (both in mm) to the corresponding fields of the Tools Menu -> Camera Calibration window prior to processing according to the camera specification. (sensor pixel size is usually about 0.004 mm, so it shouldn't be confused with the image resolution in pixels).