.Renviron variables not found when Rscript run from powershell?

I have an R script that runs perfectly when run from Rstudio. It uses an .Renviron file to provide environment variables which are visible in Sys.getenv() (so I know it works).

However, when I run the exact same script via powershell, the R script mysteriously doesn't find those environment variables (I confirmed this by print(Sys.getenv()) - the environment variables provided through .Renviron are nowhere to be seen.

Question

Why aren't the .Renviron variables being found when the R script is run from powershell (as opposed to when the script is run in RStudiom, where everything works)

What I've tried

The .Renviron file is currently saved in "C:/Users/Administrator/Documents/.Renviron"

Inspecting normalizePath(Sys.getenv('R_HOME')) returns "C:\\Program Files\\R\\R-3.6.0", so I also tried putting .Renviron there. No luck

Based on this I also tried Sys.getenv("C:/Users/Administrator/Documents/.Renviron"), but again no luck

This is what worked for me

path_to_Renviron_file <- "C:/Users/Administrator/Documents/.Renviron"
readRenviron(path_to_Renviron_file)