Most technical issues can be solved by a quick restart. This video shows you how to manually reset the Electrified S2 & X2 if your bike gets stuck.
Look under the bike's top tube at the area beneath the Matrix Display. You'll see the plastic speaker grill, with a small circular hole at the end nearer the handlebars. Insert a small tool (like a pen or paperclip) into this hole and push until you hear a clicking sound. Remove the tool – the bike has now been reset and should function as normal.