mrgsolve not running in R version 3.5.1

[Pesi2018]

Could you please help in solving the problem I am encountering when running mrgsolve in R version 3.5.1. I ran the commonly used example and still get an error message below:
mod <- mread("pk2", modlib())
Compiling pk2 ... Warning message:
In system(cmd) : 'make' not found

Error: there was a problem building the model.

[japineiro]

This just happened to me. The following steps solved the issue for me:

1. Downloaded the newest Rtools package (which is Rtools43) here https://cran.r-project.org/bin/windows/Rtools/
2. Update R to the newest version.
   After these two steps, it worked fine, I'm not sure if they will fix the problem for you, but try.