Problems with R 4.0.0 - Windows - "Error: package or namespace load failed for ‘stats’ in inDL(x, as.logical(local), as.logical(now), ...):"

Hi! thanks for your answer.
Trying the command indicated do not launch any changes.
However, I think that I just figure out what happened: Rtools4.0.0 has a created the conflict (here), By changing the PATH, as the instructions suggest, creates a conflict with base R packages. I use this to reset the PATH and that prior message didn't appear anymore.
But, Rtools 4.0.0 sends this message by installing or updating packages:

install.packages("jsonlite", type = "source")
WARNING: Rtools is required to build R packages but is not currently installed. Please download and install the appropriate version of Rtools before proceeding:

Did I do something wrong?