I have uninstalled R, RTools and RStudio, and fresh re-installed.
The error
Error in mutate() :
In argument: stlf = (function (object, ...) ... .
Caused by error in .mapply() :
! argument "MoreArgs" is missing, with no default
Run rlang::last_trace() to see where the error occurred.
seems to be because of the development version of package distributional remotes::install_github("mitchelloharawild/distributional") , installed because I had a sqrt function error fable and distributional packages: hilo() function error. If I install the CRAN version package distributional I do not get the .mapply() error.