Can't transform a data frame with duplicate names

General
2

This must not be my day...
I am getting the same error with a mutate command:

tmp_data <- apidata %>%
           mutate(geoid = paste0(state,county)) %>%
          filter(geoid %in% ctyFips)

returns

Error in `mutate()`:
! Can't transform a data frame with duplicate names.
Run `rlang::last_error()` to see where the error occurred.

is this a dplyr problem?
AB