Could you please run similar command as below?
In Tlt-convert for custom trained YoloV4 model failed on Jetson Nano 4G - #34 by Morganh , I generate fp16 trt engine successfully in Nano.
$ ./tlt-converter -k nvidia_tlt -d 3,544,960 -e trt.fp16.engine -t fp16 -p Input,1x3x544x960,1x3x544x960,2x3x544x960 yolov3_resnet18.etlt