Forecast with other time series

[MarleneBs]

I have saved a trained model. I have trained the model with time series 1, 2 and number 3 and now want to use the trained model elsewhere to forecast a time series number 4. Is that possible, it should be, right? I just put in another ZR for testing. But somehow this takes an excessive amount of time. I've been waiting here for 20-30 minutes, and before that, the forecast itself always went within seconds. Where is the problem?