Can't figure out error Data Cleaning with R 6/14

Screen Link:

My Code:

ap_2010 <- read.csv("ap_2010.csv")
library(purrr)
map(ap_2010, class)
library(dplyr)
ap_2010 <- ap_2010 %>% mutate(across(`AP.Test.Takers`: `Number.of.Exams.with.scores.3.4.or.5`, as.numeric)) %>% mutate(exams_per_student = `Total.Exams.Taken` / `AP.Test.Takers`) %>% mutate(high_score_percent = (`Number.of.Exams.with.scores.3.4.or.5`/ `Total.Exams.Taken`) * 100)

What I expected to happen:
When I ran this code, I did get the output I expected - the revised data frame with 2 new columns with the values - even with the error codes for the three variables in this pattern:

Warning message:
“Problem with `mutate()` input `..1`.
ℹ NAs introduced by coercion
ℹ Input `..1` is `across(AP.Test.Takers:Number.of.Exams.with.scores.3.4.or.5, as.numeric)`.”
Warning message in fn(col, ...):
“NAs introduced by coercion” 

What actually happened:
I get the expected outcomes, but when I click “Submit Answer”, I get this:

Running your code caused an error.
ap_2010 is a data.frame, but we expected it to be a ['spec_tbl_df', 'tbl_df', 'tbl', 'data.frame'].

I don’t understand why I am getting this error. Any suggestions/assistance are appreciated!