In the current version of Rstudio, 1.3.1056, i seem to be having problems with the Assignment operator shortcut (Alt+"-"). This shortcut isn't working anymore using the "-" on the numeric keypad, but it still works fine using the "-" in the typing key group. Here's the session info.
R version 4.0.2 (2020-06-22)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 18363)
I'm not an expert but all the times I've had problems with shortcuts including the ALT key was because there were another program interfering with that shortcut. Maybe you have installed recently a different program that could use that combination of keys?
Thank you for the reply!
Unfortunately i've tested it on three different machines running windows 10 and they all have the same problem with Rstudio 1.3.1056 . Furthermore, the problem disappears when i downgrade to Rstudio version 1.2.5042 on all of them. I'm guessing you're not using windows 10 youself?