Apply again at the right time

If your citizenship application was refused, your best option may be to wait and reapply.  It depends on the reason Immigration, Refugees and Citizenship Canada (IRCC) refused your application.

For example, if they refused it because you don't meet the residency requirement, you might want to wait and reapply after spending more time in Canada.

Or, if they refused it because you don't meet the language or knowledge requirements, you might want to wait until you're 55 years old, if that's not too long to wait. People who are 55 years or older don't have to meet the language or knowledge requirements.