Neural network not training - matlab

Question

I'm trying to set up a custom neural network, but when I train it, it doesn't train : the training process makes 0 iterations! I don't get any errors though, just 0 iterations, and I have no idea why. (The architecture might seem odd to you, it is supposed to be a custom PNN. But before we can even discuss if it makes sense or not, I would like to be able to train it...)
Here is the code
net = network;
net.trainFcn = 'trainlm';
net.performFcn = 'mse';
net.numInputs = 1;
net.numLayers = (2*nbclasses)+1; % (one pattern layer + one summation layer per class) + competition layer
net.inputConnect(1:nbclasses,:) = 1; % connects the input to all pattern layers
for i = 1:nbclasses % Connect the pattern layers to their corresponding summation layers
net.layerConnect(i+nbclasses,i) = 1;
net.layers{i}.size = size(tr_feature,1);
net.layers{i}.transferFcn = 'radbas';
end
for i = (nbclasses+1):(nbclasses*2) % Connect all summation layers to the competition layer
net.layers{i}.size = 1;
net.layerConnect(net.numLayers,i) = 1;
end
net.layers{net.numLayers}.transferFcn = 'compet';
net.outputConnect(1,end) = 1;
net.view;
[net, tr] = train(net,tr_feature',tr_true');
% tr_feature is a 800x2 data matrix, tr_true is the 800x1 corresponding labels
Any idea?
Thanks in advance!