I am also having this issue with my RStudio Cloud, running on Google Chrome, as well. It does not matter which project / workspace I go into, I am having the same issue.
Even when pressing the built in shortcut to open terminal Alt + Shift +T it will not open.
Force quitting and restarting the R session did not work me for me, nor did resetting the session to an earlier update.
Did not have this problem yesterday; only this morning. Unfortunately, because of logging out and trying to restart the session NONE of my projects will load. 