Thank you for updating, checking, and for letting us know.
Sorry to hear that did not fix the situation for your Mac.
Re: "The text box is not there. I can read messages but not answer."
If you haven't tried this already : Try re-sizing the Messages window to be less tall, and lift the window up, in case the text box has just slipped out of sight, below the bottom of the screen.
Else: You might want to send feedback to reach those who work on the software behind-the-scenes at Apple.
They will likely not reply, yet your feedback will be carefully read and logged. If others have a similar issue, there will most likely be another update that addresses the issue. The more info. Apple receives on which hardware models and software versions are affected, the more likely there will be an update that fixes the issue. (You could include a link to your post here in the community, if you wish.)
Web-form for feedback: Feedback - Messages - Apple