As we cannot reproduce the error on our side because you did not provide a reproducible example, I can just give you hint of possible issues. Please provide a reprex if you want us to help you more easily
When you see some difference between a code running in the R session, and not running when clicking on the Knit button, you should take a look at the environment. You must have in mind that a Rmd when render with the IDE button is knitted in a new clean R session. Sometimes, there could be differences if you have some stuff in your workspace that are not yet reproduced in your Rmarkdown file. For example, if data does not containes Gender, or if a library is not loaded properly.
I could not be that at all but I just was i though reading your issue.
If you can provide more context on the error or a reproducible example, we could help more. Thank you !