Input shape in a multivariate RNN
Ok... Take a step back. When you're dealing with RNNs your dataset should have a shape that looks like (nb_samples, nb_timesteps, nb_features)
Translating this to your use case means that each account is a sample (what you'll iterate when doing mini-batching), each week is a timestep (what your rnn will iterate over) and your features are.... Features.

Now... Don't use accountID as a feature. That's just an ID with no prediction power. Also try to add some seasonality features, like month or something.
Does that help you out?