I've run into the same issue with Sublime suddenly failing to send R code as this user, as well as the one they link to. In the past their workaround, i.e. killing and restarting the REPL or uninstalling/reinstalling SendText and SendCode, have addressed the issue, but so far no luck today.
I've also heard of the "R for windows terminal front end" zombie issue described here, but my task manager doesn't show anything out of the ordinary. Any other suggestions? I really don't want to go back to RStudio haha.