I have had this problem before, and in my case, it was one of the following problems each time:
- Bad network connection. Sometimes, my old internet connection would get spotty, and I would get this error if the repository was connected successfully but the connection was interrupted while transferring the repository contents.
- Out-of-date repository. All repositories are not updated together, since each is managed by a different individual/group/organization. Switching repositories can get you a different selection of packages and with different versions.
- Out-of-date R version. I notice you're running a version of R that is several versions older than the current stable. Some packages do not seem to display for certain versions of R. I think this has to do with some dependency listing within the package. Updating may fix this.
Good luck!