Fun fact: German ICEs (high-speed trains) are not allowed to enter Switzerland if they are delayed too much so they don't disrupt the Swiss schedule. This year more than 10% were not allowed to continue.
In Austria they're not as direct as this, but usually say "because of delays abroad" which is easily decipherable as these trains usually travel from Germany.
I went to switzerland two times via train the last few years (usually I go with my dad by car), and both times this happened. Once we had to sleep there overnight, because after we got in with another train, there were no more trains through the mountains.