⇒The student enter Taiwan without the visitor visa/ with landing visa
⇒You’re holding the visitor visa, but you can’t extend it if 

*Your passport will be expired within six months
* You have had your visitor visa expired before
* You have extended your visitor visa twice (the maximum duration of stay for visitor visa is 180 days)
* Your visa has expired.
* You’d like to extend your visa because you can’t book your flight
* You need medical treatment because chronic disease