Currently Northern Rail train crew are having an unannounced overtime ban every Sunday (yesterday was the 3rd in a row) leading to many cancellations.
Yesterday the resulting train crew shortage was so severe that a region wide Do Not Travel (DNT) notice was issued during the afternoon.
Some routes closed in the early evening, and the DNT was issued because Northern were unable to source other transport.
So for the time being, if travelling anywhere on Northern on a Sunday, travel as early in the day as possible. Other operators in the region are not affected.