Trying to use "pak" to install an R source library from a private CRAN-like repo

Question

I'm trying to use "pak" to install an R source library from a private CRAN repo (hosted with Artifactory) and I haven't been able to figure out how to get it to work. I start with a conda enviroment like so:

conda create --name testing_r_pak --channel=conda-forge r-base=4.1.0 r-essentials=4.1.0
conda activate testing_r_pak
Rscript -e 'install.packages("pak", repos = "http://cran.us.r-project.org")'

and then run the following to try and install my R package, along with deliver some troubleshooting info:

Rscript -e 'options(width=400); print(pak::repo_status()); pak::pkg_install("TestRPackage")'

Here's the result:

# A data frame: 6 × 10
  name          url                                                         type     bioc_version platform path        r_version ok     ping error 
  <chr>         <chr>                                                       <chr>    <chr>        <chr>    <chr>       <chr>     <lgl> <dbl> <list>
1 pvt_cran      https://<pvt_cran_repo_url>/                                cranlike NA           source   src/contrib 4.1       TRUE   1.05 <NULL>
2 CRAN          https://cran.rstudio.com                                    cran     NA           source   src/contrib 4.1       TRUE   1.05 <NULL>
3 BioCsoft      https://bioconductor.org/packages/3.14/bioc                 bioc     3.14         source   src/contrib 4.1       TRUE   1.05 <NULL>
4 BioCann       https://bioconductor.org/packages/3.14/data/annotation      bioc     3.14         source   src/contrib 4.1       TRUE   1.06 <NULL>
5 BioCexp       https://bioconductor.org/packages/3.14/data/experiment      bioc     3.14         source   src/contrib 4.1       TRUE   1.23 <NULL>
6 BioCworkflows https://bioconductor.org/packages/3.14/workflows            bioc     3.14         source   src/contrib 4.1       TRUE   1.25 <NULL>
✔ Loading metadata database ... done

Error: <callr_remote_error: Cannot install packages:
* TestRPackage: Can't find package called TestRPackage.>
 in process 21027 
-->
<simpleError: Cannot install packages:
* TestRPackage: Can't find package called TestRPackage.>

 Stack trace:

 12. (function (...)  ...
 13. base:::withCallingHandlers(cli_message = function(msg) { ...
 14. get("pkg_install_make_plan", asNamespace("pak"))(...)
 15. prop$stop_for_solution_error()
 16. private$plan$stop_for_solve_error()
 17. pkgdepends:::pkgplan_stop_for_solve_error(self, private)
 18. base:::stop("Cannot install packages:\n", msg, call. = FALSE)
 19. base:::.handleSimpleError(function (e)  ...
 20. h(simpleError(msg, call))
 21. base:::stop(e)
 22. (function (e)  ...

 x Cannot install packages:
* TestRPackage: Can't find package called TestRPackage. 

Execution halted

Some notes:

• I know I have a correctly constructed .Rprofile with my private CRAN repo added into it. As you can see, pak::repo_status() even sees it correctly.
• I know I have a properly functioning private CRAN repo because running Rscript -e 'install.packages("TestRPackage", repos = "https://<pvt_cran_repo_url>")' in the same conda environment works fine.
• I've tried a few different versions of R with the same result.
• I've tried this on a couple of different hosts (Mac, Ubuntu) with the same result.
• I've also tried this without conda, with the same result.

I'm pretty stumped here - I hope it's something obvious I'm missing, but I'm not sure what else to do. I'd appreciate any help.