I’ve never seen this on these boards, usually, if you’re logged in (and are you?), you can leave a reply by scrolling down, much as I’ve done here. Off hand, if you’re not logged in, I thought the ‘reply’ button would take you to the login page, and then back to the post after you’ve replied. 

As another thought, any chance you have some sort of app that might be blocking this function? Some sort of ‘ad blocker’ or K-pop up blicker’ that is interfering with the process? What device and browser are you using to read/ reply in these forums?

As a note, in order to post your question, you are indeed logged in… which is why that second paragraph. 

After I closed and re-entered from the email I have a reply box!

Ralph