I have to admit I don't see a problem but Ican not tell from the screenshot exactly where the error is occuring
Does
View(penguins)
work okay?
My version of your code seems to work well.
library(ggplot2)
library(palmerpenguins)
View(penguins)
ggplot(data = penguins) +
geom_point(mapping = aes(x = flipper_length_mm, y = body_mass_g))