What does the error requires complex weights in neural nets mean




While applying neural net on a dataset I got stuck due to an error:

neural <- neuralnet(label ~ pixel0-pixel783,train,hidden = 500,threshold = 0.1)

Not sure what this error means and cannot figure out how to resolve this.
Can someone please help me with this??
Also in neural nets can’t we give label ~ . like in random forests which will basically predict the label based on all other attributes in data.I had tried it but got an error: