Currently, due to heavy usage (more than 20 sequences/day on average) because of the CASP experiment, the tertiary structure modelling server modules are quite slow in returning models.
Please read the documentation as well as some caveats based on the analysis of the server modules' performance before submitting a sequence. In particular, please do realise that the de novo approach is best only for smaller sequences (100 amino acids or less). Also, users submitting a large number of sequences simultaneously will be moved to a separate queue which would be (naturally) slower).
Check current prediction status of your job.