Threads are closed automatically when they have not received a response after a certain period of time - three months, I think. Check the date of the last post. You can always start a fresh thread on the topic if you wish.
Moderators occasionally close a thread earlier for some reason that they normally give when they close it.
ps (later). I have just come across a recent thread which has been closed without a reason being given. If one looks at the comments from the OP to some of the people who have attempted to be of assistance, one can guess that a mod has closed the thread to preserve harmony in the forum.
Retired English Teacher