I am also getting this error in my projects and my students' projects. This does not look like something that is fixable from the user end.
I'd suggest contacting your instructor to let them know about the issue, especially if they are paying the instructor fee and can open another official support ticket on the issue.
We found a solution now. If you change the R-version in the upper right corner (below your name) from "R 4.1.3" to "R 4.2.1", you are asked to install some packages. After doing so everything works as it used to.
Sorry for the delay. We recently upgraded the version of the RStudio IDE used by RStudio Cloud and accidentally introduced a bug with pandoc. The bug was fixed a couple days later but there was a brief window (a little over a day) where the error you saw would have happened for some projects.
Sorry for the issues this caused and the delay in responding.