Why can't I reply to any posts?

The "locked thread" banner looks like this:

If you came here from a search engine, those will almost always direct you to older threads because they index everything, sometimes even threads over 10 years old. Your question is almost identical to those asked here by people who use a search engine to find forum questions to answer.

Threads seem to get lock after 3-6 months.

I've been here a very long time and understand this: people who post a question almost never return weeks or month later to check for responses. You are most effective here by working the first page ( or 2-3 pages if a busy forum like iPhone) of each section's topic list.

Please bookmark this handy tool. This site map has links that take you directly to the most current version of the topics list for each forum section available.:

Site Map - Apple Community

Your second screenshot appears to be an older thread, as such it may be locked due to inactivity. If so, it should show that at the top of the thread. Also, the error message you show can sometimes be cleared by refreshing the page, then attempting to reply again.

What happens if you click on the blue "Reply" button?

Are you trying this on your computer or iOS device?

Any Pop-Up or Add blocker installed?

No, that should not be a "Level 1" issue.