Hi Steve - looks like you are installing dplyr into the "U:/Documents/R/win-library/3.5" directory, but then loading tidyverse from the "C:/Program Files/R/R-3.5.1/library" directory. So the new dplyr you installed isn't being called - the one in "C:/Program Files/R/R-3.5.1/library" is. If you want to have your packages located in "C:/Program Files/R/R-3.5.1/library" there are a couple of things you could try:
install.packages("dplyr", lib = 'C:/Program Files/R/R-3.5.1/library')
library("tidyverse", lib.loc="C:/Program Files/R/R-3.5.1/library")
If you are still having trouble with that, I'd just try to redownload the tidyverse packages using
install.packages("tidyverse", lib = 'C:/Program Files/R/R-3.5.1/library')
library("tidyverse", lib.loc="C:/Program Files/R/R-3.5.1/library")
cheers.