I am trying to download these instruments and it has just been stuck on downloading for the last day now.
Mine did that too! It was some nonsense about the store not syncing correctly, and the items had indeed actually downloaded! Start a couple of new channels and see if you can add the instruments that don't seem to be downloading. If they play correctly, they're obviously downloaded, in the real world. I read up and found a few options about clearing the cache, or changing out settings, but the problem was that there was no problem, just the store/downloads listing the status incorrectly. :/
Usually, quitting Native Access, restarting your computer allows you to download again. Did that work out?
I meant that they were still stuck on the Installing phase, and even then it did not really do anything
I'm not sure to follow. Did restarting the computer worked or not? If you still struggle with tis you should get in touch with my colleagues here: https://bit.ly/NI_Support_All