I'm using devtools install monocle3 from github, but it didn't work
> devtools::install_github("aertslab/SCENIC")
Using github PAT from envvar GITHUB_TOKEN
Error: Failed to install 'unknown package' from GitHub:
Failed to connect to api.github.com port 443: No route to host
Your issue seems to be that you have issues with network connections (maybe you are behind a network firewall) that prevent you to reach api.github.com on port 443 (https).
You can either fix your network connection/firewall or alternatively download the package from https://github.com/aertslab/SCENIC/releases/download/v1.1.2/SCENIC_1.1.2.tar.gz on a different server and copy it to your RStudio Server. There is a risk that this package depends on other R packages though. As a consequence the installation of those dependencies could fail for similar reasons than the devtools::install_github().