If you miss the deadline to respond to an office action, the consequences will depend on the specific jurisdiction and the nature of the office action.
In general, if you do not respond to an office action within the given deadline, your trademark application may be considered abandoned. This means that your application will no longer be active, and you will not be able to obtain a trademark registration based on that application.
However, some jurisdictions, e.g. the USA, offer a grace period during which you can still revive your application. To do so, you would need to file a petition or request to revive your abandoned application and provide a valid reason for missing the deadline.
It's important to note that missing a deadline can be costly and time-consuming. It's always best to respond to office actions in a timely manner, and if you are unsure about how to proceed, consult with a trademark attorney who can guide you through the process.