Please be aware there is a four day holiday starting on Thursday (5 April). That may make booking train tickets difficult.
I have never tried to book train tickets online so I can't really help you much there.
As for alternative ways of getting to Taichung there are lots of buses that run. The buses take about two hours if the traffic is not heavy. There is an intercity bus station near Taipei Main Station (west side) and buses for Taichung also leave from a few other places around the city.
buses to Taichung
Please be aware there is a four day holiday starting on Thursday (5 April). That may make booking train tickets difficult.
I have never tried to book train tickets online so I can't really help you much there.
As for alternative ways of getting to Taichung there are lots of buses that run. The buses take about two hours if the traffic is not heavy. There is an intercity bus station near Taipei Main Station (west side) and buses for Taichung also leave from a few other places around the city.