This is affecting /u/lindasenora. I invited her via reddit, she joined a few days ago, and now says:
I was able to open an account, but I have been unable to participate in any of the discussions. When I try to post a comment, I get an Error message.
I know some others who've joined in the last few days and haven't posted either, so maybe the error is stopping them too? Hopefully admins can look into it ASAP.
(I've asked for more details about the error message, and suggested that she take a screenshot and PM it to admin)
Can you find out what device and browser /u/lindasenora is using, and ask her to try a different browser and see if the same thing happens?