It seems there is a problem with getting all the package versions in the correct state. This can happen occasionally, and probably the best way of dealing with that is to systematically install every package that causes a problem.
In your case it seems you should re-install fs:
install.packages("fs")
Keep installing all the packages you need until everything is resolved.
(One thing to look out for is that you don't accidentally have to R sessions open, e.g. multiple RStudio windows. A second R session will block your package installation process.)