error reoccurring in code that uses dplyr package

this is my code:

lcdf %>%
  group_by(purpose) %>%
  summarise(
    nLoans=n(),
    defaults=sum(loan_status=="Charged Off"),
    avgInterest= mean(int_rate),
    avgLoanAMt=mean(loan_amnt)
  )

I get this error:

Error: `n()` must only be used inside dplyr verbs.

What do I do? Thanks!