R tells me <the "sticker" function could not be found>

Hello everyone, I have installed the hexSticker and tidyverse packages but when I try to replicate the example from https://github.com/GuangchuangYu/hexSticker, I receive the following error:
Error in sticker(~plot(cars, cex = 0.5, cex.axis = 0.5, mgp = c(0, 0.3, : 
function "sticker" could not be found. 

If you could help me to fix this bug, I would be very grateful.