Hi Thank you for your question. You should be able to do this, but I appreciate the issue that you are having. Some add-ons can take some time to download (depending on your connection speed) and it may appear that they are no downloading, but if you give it a little time, they will download and install without an issue. I hope this helps, but if not, please come back here with details of the add-on that you are trying to use and we can take another look at it.