Howdy Kieunnia,
I would love to help you with this.
It seems like your theme’s default template might not be compatible with The Events Calendar. But don’t despair, usually switching templates within your theme solves the issue quite easily. To do this go to WP-Admin > Events > Settings > Display . Do you see the Template dropdown ? It’s probably set to Default Events right now. Try selecting a different one and hitting Save, then view the front end. Does that fix things? Try this for each template form the dropdown to see if any of them work, likely a few willl and you can choose the one you like best.
Does that all make sense? Will that work for you? Please let me know.
Cheers!
– Brook