Error when trying to make cluster using R (Rscript execution error: No such file or directory)

Hello and thank you for your time.
I get the error:

cl <- parallel::makeCluster(2)
Rscript execution error: No such file or directory

whenever I try to make a cluster using the package "parallel". Other commands such as detectCores() work, but makeCluster() fails. I have reinstalled R and Rstudio, and I do not think the problem is with the installation.

R version 3.6.2 (2019-12-12)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.3 LTS

Any help would be appreciated.

UPDATE:
If I run Rscript in the terminal, I get a similar error, but if I use sudo Rscript the error goes away. For example: Rscript helloworld.r gives me the error Rscript execution error: No such file or directory, but sudo Rscript helloworld.r works. (helloworld.r is an R script that prints hello world.)

Thanks in advance.