This is a recent issue with some GVL builds. Could you start a new GVL and allow the services to build (approx 20 mins). If Rstudio/Jupyter have not built then please reboot the instance and allow a few minutes for them to finish building. Do not update the instance before Rstudio has built. If that does not resolve the issue let me know and I will provide further support.
Sion, thank you for the suggestion, but I am afraid I could not get it to work on the day. I did manage to find a workaround (with the help of someone more in the know about things than me!) by comparing the file structure of the nginx folder between a VM that worked and the one that didn’t. When we copied over the files that were not reset properly after unshelving, I was able to launch RStudio just in time for the students to use on the course I was running on Tuesday afternoon.
Not sure whether this was the best way to go about it, and whether it will cause any problems in the future, but it worked!