Hi,
This question is for shinyapps.io. and should be asked in https://forum.posit.co/tags/c/shiny/shinyappsio channel.
Usually it's caused by an internal proxy you are going through which injects its own certificate. You can verify by checking for http_proxy and https_proxy in the IDE env. If there, you can unset with:
Sys.unsetenv("http_proxy")
Sys.unsetenv("https_proxy")
and try to deploy again then re-set the variables.
Thanks for reaching out to the team.