Offline install methods not working

[SallyJohnson]

Occasionally we have to download zip files for other R package repos and we can install them with devtools, and sometimes even just install.packages(.....)

However the rstan zip file seems to be different format and all attempts to install from it fail.

Is there anything different about it?

[andrjohns]

Closing this issue for now, feel free to reopen if there's still an issue