Loss value not decreasing and predictions are constant for regression model

I am doing a transfer learning using USE to train quora question pairs for similarity using a Siamese network.
When I am training I am getting almost constant loss, not decreasing nor increase, also when I predict after train, all predictions value are same.
Can someone please help? I am stuck on this issue since last 2 days!

Here is the colab notebook link.

Your notebook requires a permission to access it. Could you post an “open” link so that we could check it for errors?


Let me know if you can access it?

Yes, I can access it, thanks.
I don’t see any obvious errors and the model is generally able to learn random data:

model = torch_siamese()
data1 = torch.randn(64, 512)
data2 = torch.randn(64, 512)
target = torch.randn(64, 1)
optimizer = torch.optim.Adam(model.parameters(), lr=1e-2)
nb_epochs = 100

for epoch in range(nb_epochs):
    output = model(data1, data2)
    loss = loss_func(output, target)
    print('epoch {}, loss {}'.format(epoch, loss.item()))

I would recommend to check the shapes of the output and target tensors and make sure they are equal. Sometimes unwanted broadcasting could be applied if e.g. the target is missing a dimension, which would result in this bad training performance.