I came across a closed out issue that is yet to be resolved. see here>> https://community.rstudio.com/t/i-can-install-lubridate-in-r-but-i-can-not-in-rstudio-i-am-newby/156787?u=mezixs_filz
My solution on this is , first ensure that you installed the tidyverse package correctly.
secondly, attach core tidyverse packages using the <_library(tidyverse) command/ prompt
lastly, check if the lubridate package is checked in the response from your command
if checked, there is no need to initiate another command to attached lubridate packages.
to ensure that the lubridate package is attached, go to the bottom right pane, and select the package table, in the search button by the right corner, search all the packages listed in the response to your tidyverse command/ prompt and confirm they are checked. if the lubridate package is checked, that validates that it is already attached.
kindly view the attached for clarity.