Authentication using for rdrop2

I'm attempting to set up dropbox on a virtual machine (digital ocean droplet) using the rdrop2 package to a newly-created dropbox scoped app. This will be a persistent data repo for a shiny app.

Please note that this is a duplicate cross post to an issue filed at the project's github page. Thank you in advance for any troubleshooting advice.

For this app, I have a key, secret, and token, all taken from the Dropbox developer console page.

If I simply copy/ paste the token to my remote machine and run something like:

token <- "my_token_string" 
saveRDS(token, "drop_token.RDS)
rdrop2:: drop_auth(rdstoken = "drop_token.RDS")

...this does nothing.

The helpfile for the rdstoken argument to the drop_auth function says:

"In server environments where interactive OAuth is not possible, a token can be created on a desktop client and used in production."

The ReadMe says:

If you expect to access a Dropbox account via Shiny or on a remote cluster, EC2, Digital Ocean etc, you can leave the cached oauth file in the same directory, or pass the token explicitly to drop_auth. You can also save the output of drop_auth into an R object, sink that to disk, and pass that as a token.

So I have a token in hand, but I don't know how to pass it.

Something else I tried

From a local machine (ie with a browser), I attempted

drop_auth(new_user = F, key = MY_APP_KEY, secret = MY_APP_SECRET)

This results in the following error in a browser window (400 error):

_**"More details for developers

Invalid redirect_uri. It must exactly match one of the redirect URIs you've pre-configured for your app (including the path)."**_

Note that I've added both https://localhost and http://localhost as redirect URIs on the DB console.

Account Type

Dropbox Plus.

Session Info for the VM

> devtools::session_info()
─ Session info ───────────────────────────────────────────────────────────────
 setting  value                       
 version  R version 4.0.0 (2020-04-24)
 os       Ubuntu 18.04.4 LTS          
 system   x86_64, linux-gnu           
 ui       X11                         
 language (EN)                        
 collate  C.UTF-8                     
 ctype    C.UTF-8                     
 tz       Etc/UTC                     
 date     2020-09-14                  

─ Packages ───────────────────────────────────────────────────────────────────
 package     * version date       lib source                         
 assertthat    0.2.1   2019-03-21 [1] CRAN (R 4.0.0)                 
 backports     1.1.6   2020-04-05 [1] CRAN (R 4.0.0)                 
 callr         3.4.3   2020-03-28 [1] CRAN (R 4.0.0)                 
 cli           2.0.2   2020-02-28 [1] CRAN (R 4.0.0)                 
 crayon        1.3.4   2017-09-16 [1] CRAN (R 4.0.0)                 
 desc          1.2.0   2018-05-01 [1] CRAN (R 4.0.0)                 
 devtools      2.3.0   2020-04-10 [1] CRAN (R 4.0.0)                 
 digest        0.6.25  2020-02-23 [1] CRAN (R 4.0.0)                 
 ellipsis      0.3.1   2020-05-15 [1] CRAN (R 4.0.0)                 
 fansi         0.4.1   2020-01-08 [1] CRAN (R 4.0.0)                 
 fs            1.4.1   2020-04-04 [1] CRAN (R 4.0.0)                 
 glue          1.4.2   2020-08-27 [1] CRAN (R 4.0.0)                 
 httr          1.4.2   2020-07-20 [1] CRAN (R 4.0.0)                 
 magrittr      1.5     2014-11-22 [1] CRAN (R 4.0.0)                 
 memoise       1.1.0   2017-04-21 [1] CRAN (R 4.0.0)                 
 pkgbuild      1.0.7   2020-04-25 [1] CRAN (R 4.0.0)                 
 pkgload       1.0.2   2018-10-29 [1] CRAN (R 4.0.0)                 
 prettyunits   1.1.1   2020-01-24 [1] CRAN (R 4.0.0)                 
 processx      3.4.2   2020-02-09 [1] CRAN (R 4.0.0)                 
 ps            1.3.2   2020-02-13 [1] CRAN (R 4.0.0)                 
 R6            2.4.1   2019-11-12 [1] CRAN (R 4.0.0)                 
 rdrop2        0.8.2.1 2020-09-12 [1] Github (karthik/rdrop2@6176b86)
 remotes       2.1.1   2020-02-15 [1] CRAN (R 4.0.0)                 
 rlang         0.4.7   2020-07-09 [1] CRAN (R 4.0.0)                 
 rprojroot     1.3-2   2018-01-03 [1] CRAN (R 4.0.0)                 
 sessioninfo   1.1.1   2018-11-05 [1] CRAN (R 4.0.0)                 
 testthat      2.3.2   2020-03-02 [1] CRAN (R 4.0.0)                 
 usethis       1.6.1   2020-04-29 [1] CRAN (R 4.0.0)                 
 withr         2.2.0   2020-04-20 [1] CRAN (R 4.0.0)