It is very unlikely that this is related to R or RStudio, since you are using a relative path, start by making sure your working directory is set where you think it is, run getwd() and see if it returns the folder where "timelinetest.csv" is stored.
Also, you could use an absolute path to reference the files to avoid any possible confusion.
Some cloud memory like Dropbox automatically moves dormant files to the cloud and RStudio then fails to find them, beven though the file is listed in a local synced directory.
I've tested the working directory, but I guess you're right. This seems not related to RStudio. I was able to read the .ods file, although I still don't know what was wrong.