I have similar issue when using laptop from my university. The RStudio-Quatro shortcut for inserting new chunk of code (Ctrl + Alt + i)) doesn't work because the university has set that shortcut to open a certain application and I may not have an authority to change the shortcut setting.

However, I can still use (Alt + c) shortcut to access "Tabs bar" --> "Code", in which the "Insert chunk" is luckily the first option there. So, the next step is to just press "Enter", then I will get similar result.

So, the alternative I always use is: (Alt + c) then "Enter", when (Ctrl + Alt + i) doesn't work.