I solved my issue and post it here for future new users trying to follow the tutorial.
There is an error in the tutorial source example in the NormalizationHybridLayer class declaration. The line that reads
init=mx.init.Constant(scales.asnumpy()),
should actually read
init=mx.init.Constant(scales.asnumpy().tolist()),
The fix is given by @thomelane in the " How to create symbol parameters?" MxNet forum thread.
It would be nice if the tutorial was fixed.