방 키가 안 돼요.

When to use

This is a common phrase to report a malfunctioning key card so the staff can reprogram or replace it.

How it works

The sentence is in the polite informal register.

• 방 키가: 'Room key' + subject particle '가'
• 안 돼요: 'Does not work' (adverb '안' + verb '돼요')

Expressing Malfunction

The verb '되다' (to become/function) is extremely versatile. When combined with the negative adverb '안' (not), '안 되다' is the standard, natural way to say a machine, device, or system is broken or malfunctioning.

Notes

Use this phrase at the front desk when your room key card fails to unlock your door.