RStan no longer working one two computers

Interfaces
1

Short summary of the problem
I am not sure what has changed on my two computers, but I can no longer run Stan code through R.

Operating System: Windows 10 for both computers
R version: 3.6.1 with RTools 3.5 for computer A and 4.03 with RTools4 for computer B
Versions: OS: x86_64, mingw32; rstan: 2.21.2; Rcpp: 1.0.7; inline: 0.3.15 for both computers

Errors I get:
Computer A: COMPILING THE C++ CODE FOR MODEL ‘73fc79f8b1915e8208c736914c86d1a1’ NOW.
OS: x86_64, mingw32; rstan: 2.21.2; Rcpp: 1.0.7; inline: 0.3.15
Error in cleanup_makevar(old) :
argument “RMU” is missing, with no default
In addition: Warning message:
In system(paste(CXX, ARGS), ignore.stdout = TRUE, ignore.stderr = TRUE) :
‘c:/Rtools/mingw_/bin/g++’ not found

Computer B: Compilation ERROR, function(s)/method(s) not created!
Error in compileCode(f, code, language = language, verbose = verbose) :
C:/rtools40/mingw64/bin/…/lib/gcc/x86_64-w64-mingw32/8.3.0/…/…/…/…/x86_64-w64-mingw32/bin/ld.exe: C:/Users/bh188799/Documents/R/win-library/4.0/rstan/lib/x64/libStanServices.a(stan_fit.o):stan_fit.cpp:(.data$_ZZN5boost4math6detail9bessel_j0IeEET_S3_E2P1[ZZN5boost4math6detail9bessel_j0IeEET_S3_E2P1]+0x0): multiple definition of boost::math::detail::bessel_j0<long double>(long double)::P1'; file506c272ed3d.o:file506c272ed3d.cpp:(.rdata$_ZZN5boost4math6detail9bessel_j0IeEET_S3_E2P1[_ZZN5boost4math6detail9bessel_j0IeEET_S3_E2P1]+0x0): first defined hereC:/rtools40/mingw64/bin/../lib/gcc/x86_64-w64-mingw32/8.3.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:/Users/bh188799/Documents/R/win-library/4.0/rstan/lib/x64/libStanServices.a(stan_fit.o):stan_fit.cpp:(.data$_ZZN5boost4math6detail9bessel_j0IeEET_S3_E2QS[_ZZN5boost4math6detail9bessel_j0IeEET_S3_E2QS]+0x0): multiple definition of boost::math::detail::bessel_j0(long double)::QS’; file506c272ed3d.o:file506c272
In addition: Warning message:
In system(paste(CXX, ARGS), ignore.stdout = TRUE, ignore.stderr = TRUE) :
'C:/rtools40/usr/mingw/bin/g++’ not found

I have looked at the installation information about configuring the toolchain for Windows, and nothing is helping. I have reinstalled RStan and continue to have problems. Since RStan was working on both computers ~1 month ago, I assume that IT has changed something, but I am not sure what I am looking for.

Thanks for any help!

2

Computer A is now working although I still get the following warning:
Warning message:
In system(paste(CXX, ARGS), ignore.stdout = TRUE, ignore.stderr = TRUE) :
‘c:/Rtools/mingw_/bin/g++’ not found

Computer B is still not working.

3

To fix Computer B you just need to reinstall rstan and StanHeaders from source. For for more information, see this section of the Getting Started guide: RStan Getting Started · stan-dev/rstan Wiki · GitHub