Cant post replies to posts on the xbox forums?

I would assume that since you can now reply, ThisGameIsSucky's info has resolved your issue

Did this work?

Please mark as answered so we are able to help fellow gamers in future if we know this solutions works.

There's no limitations on how many replies you can do a day, you could potentially be trying to respond on a locked thread already, or your connection to the site may have crashed while typing the answer. If you were banned you wouldnt be able to even post
a question here i suppose.

There could possibly be a website issue, like a personal website bug. I occasionally have issues posting but I simply copy what I say, refresh the browser, then post and submit... that typically works for me. As another user had pointed out, the lock feature
is a thing normally a mod will lock a forum or thread that isn't appropriate or is locked for them to specifically help someone. That is probably not your case if you are still experiencing it here.

I would check to see if your internet browser needs an update, first. Clear your browsing history, cookies, cache, and the whole nine. Then refresh the page, exit out and reopen the browser, or try another browser all together. After that, or before that,
also check with your internet service provider to see if you are experiencing any service outages or interruptions.

Hopefully that helps.

You look if the Thread is open yet or is Loked?