Found your issue, in the .alls file, you should only be using change_output_activation with the cls layers. I adjusted the notebook to reflect the changes, but here is my .alls.
normalization1 = normalization([0.0, 0.0, 0.0], [255.0, 255.0, 255.0])
change_output_activation(conv54, sigmoid)
change_output_activation(conv65, sigmoid)
change_output_activation(conv80, sigmoid)
nms_postprocess("/content/nms_layer_config.json", meta_arch=yolov8, engine=cpu)
performance_param(compiler_optimization_level=max)