Bayes metab issues

I have tried several times to remove and reinstall rstan and stanheaders packages and I keep getting the following errors:
When trying to run the example:

> rstan_options(auto_write = TRUE)
> example(stan_model, run.dontrun = TRUE)

Compilation ERROR, function(s)/method(s) not created! Error in compileCode(f, code, language = language, verbose = verbose) : /bin/sh: line 1: C:/rtools42/mingw64/bin/g++: No such file or directorymake: *** [C:/PROGRA~1/R/R-42~1.2/etc/x64/Makeconf:260: file2b8c2ce291.o] Error 127

When trying to run the metab function:

>mm <- metab(bayes_specs, data=dat1)

Timing stopped at: 0.95 0.18 1.5
Warning message:
In metab_fun(specs = specs, data = data, data_daily = data_daily, :
Modeling failed
Errors:
invalid connection

How can I fix this?